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As filed with the Securities and Exchange Commission on July 22, 2010

Securities Act File No. 333-              

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form N-2
REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 ý

Pre-Effective Amendment No. o
Post-Effective Amendment No. o

New Mountain Guardian Corporation

(Exact name of registrant as specified in charter)

787 7th Avenue, 48th Floor
New York, NY 10019
(212) 720-0300
(Address and telephone number,
including area code, of principal executive offices)

Robert A. Hamwee
Chief Executive Officer
New Mountain Guardian Corporation
787 7th Avenue, 48th Floor
New York, NY 10019
(Name and address of agent for service)

COPIES TO:

Approximate date of proposed public offering:  As soon as practicable after the effective date of this
Registration Statement.

           If any securities being registered on this form will be offered on a delayed or continuous basis in reliance on Rule 415 under the Securities Act of 1933, other than securities offered in connection with a dividend reinvestment plan, check the following box. o

           It is proposed that this filing will become effective (check appropriate box):

           o when declared effective pursuant to Section 8(c).

CALCULATION OF REGISTRATION FEE UNDER THE SECURITIES ACT OF 1933

(1)

Includes the underwriters' option to purchase additional shares.

(2)

Estimated pursuant to Rule 457(o) under the Securities Act of 1933 solely for the purpose of determining the registration fee.

           The Registrant hereby amends this Registration Statement on such date or dates as may be necessary to delay its effective date until the Registrant shall file a further amendment which specifically states that this Registration Statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933 or until the Registration Statement shall become effective on such date as the Securities and Exchange Commission, acting pursuant to said Section 8(a), may determine.

The information in this preliminary prospectus is not complete and may be changed. The securities may not be sold until the registration statement filed with the Securities and Exchange Commission is effective. This preliminary prospectus is not an offer to sell nor does it seek an offer to buy these securities in any jurisdiction where the offer or sale is not permitted.

SUBJECT TO COMPLETION. DATED              , 2010

Shares

New Mountain Guardian Corporation

Common Stock

            This is an initial public offering of shares of common stock of New Mountain Guardian Corporation. Following this offering, we will be a holding company with no direct operations of our own, and our only business and sole asset will be our ownership of common membership units of New Mountain Guardian Holdings, L.L.C., or NMG LLC. NMG LLC will be an externally managed finance company managed by New Mountain Guardian Advisors BDC, L.L.C. and will be the operating company for our business. New Mountain Guardian Corporation and NMG LLC each intend to elect to be treated as business development companies under the Investment Company Act of 1940 prior to the completion of this offering.

            Our investment objective is to generate current income and capital appreciation through investments in debt securities at all levels of the capital structure, including first and second lien debt, unsecured notes and mezzanine securities.

            Following the completion of this offering and based on the mid-point of the range set forth herein, we will own approximately         % of the common membership units of NMG LLC and affiliates of New Mountain Capital, L.L.C. will own approximately         % of the common membership units of NMG LLC and approximately         % of our outstanding common stock, assuming no exercise of the underwriters' option to purchase additional shares.

            All of the                  shares of common stock offered in this offering are being sold by us. After giving effect to the formation transactions, the net asset value of our common stock on                , 2010 (the last date prior to the date of this prospectus on which net asset value was determined) was approximately $             per share on a fully diluted basis. Prior to this offering, there has been no public market for our common stock. It is currently estimated that the initial public offering price per share will be between $             and $             . We intend to apply to list our common stock on the New York Stock Exchange under the symbol "NMTG".

            Investing in our common stock is highly speculative and involves a high degree of risk. See "Risk Factors" beginning on page 29. This is an initial public offering, and there is no prior public market for our shares of common stock. Shares of closed-end investment companies, including business development companies, frequently trade at a discount to their net asset value. If our shares of common stock trade at a discount to net asset value, it may increase the risk of loss for purchasers in this offering. Assuming an initial public offering price of $              per share (the mid-point of the range set forth on this cover), purchasers in this offering will experience immediate dilution of approximately $              per share on a fully diluted basis. See "Dilution" on page 81.

            This prospectus contains important information about us that a prospective investor should know before investing in our common stock. Please read this prospectus before investing and keep it for future reference. Upon completion of this offering, we will file annual, quarterly and current reports, proxy statements and other information about us with the Securities and Exchange Commission. This information will be available free of charge by contacting us at 787 7th Avenue, 48th Floor, New York, NY 10019 or by telephone at (212) 720-0300 or on our website at www.newmountainguardian.com. Information contained on our website is not incorporated by reference into this prospectus, and you should not consider that information to be part of this prospectus. The Securities and Exchange Commission also maintains a website at www.sec.gov that contains such information.

            Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

(1)

All expenses of the offering, including the sales load, will be borne by NMG LLC. NMG LLC will incur approximately $        million of estimated expenses in connection with this offering. Stockholders will indirectly bear such expenses through our ownership of common membership units of NMG LLC.

(2)

To the extent that the underwriters sell more than                          shares of our common stock, the underwriters have the option to purchase up to an additional                          shares of our common stock at the initial public offering price, less the sales load, within 30 days of the date of this prospectus. If the underwriters exercise this option in full, the total price to the public, sales load and proceeds to us will be $             , $             and $             , respectively. If the underwriters exercise their option to purchase additional shares of our common stock, we will use the proceeds from the exercise of this option to purchase additional common membership units of NMG LLC.

The underwriters expect to deliver the shares against payment in New York, New York on or about                , 2010.

Prospectus dated                                        , 2010.

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          You should rely on the information contained in this prospectus. We have not, and the underwriters have not, authorized any other person to provide you with different information or to make representations as to matters not stated in this prospectus. If anyone provides you with different or inconsistent information, you should not rely on it. We are offering to sell, and seeking offers to buy, securities only in jurisdictions where offers and sales are permitted. The information contained in this prospectus is accurate only as of the date of this prospectus. Our business, financial condition, results of operations and prospects may have changed since that date. To the extent required by law, we will amend or supplement the information contained in this prospectus to reflect any material changes to such information subsequent to the date of the prospectus and prior to the completion of the offering pursuant to this prospectus.

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PROSPECTUS SUMMARY

          This summary highlights some of the information in this prospectus. It is not complete and may not contain all of the information that you may want to consider. You should read carefully the more detailed information set forth under "Risk Factors" and the other information included in this prospectus.

          In this prospectus, unless the context otherwise requires, references to:

•

"New Mountain Guardian" refers to New Mountain Guardian Corporation, a Delaware corporation, which was incorporated on June 29, 2010 in preparation for this offering;



•

"NMG LLC" refers to New Mountain Guardian Holdings, L.L.C., formerly known as New Mountain Guardian (Leveraged), L.L.C., a Delaware limited liability company, which will be the operating company for our business, and in which New Mountain Guardian will acquire common membership units in connection with this offering. NMG LLC was formed by New Mountain Capital, L.L.C. in October 2008 as a subsidiary of New Mountain Guardian AIV, L.P., or "Guardian AIV", and a co-investment vehicle, New Mountain Guardian Partners, L.P., or "Guardian Partners", was formed in February 2009. Guardian AIV and Guardian Partners are referred to collectively as the "Guardian Entities";



•

"Guardian AIV Holdings" refers to New Mountain Guardian AIV Holdings Corporation, a Delaware corporation which was incorporated on                , 2010, of which Guardian AIV will be the sole stockholder;



•

"New Mountain Guardian Advisors" or the "Investment Advisor" refers to New Mountain Guardian Advisors BDC, L.L.C., NMG LLC's investment advisor;



•

"New Mountain Guardian Administration" or the "Administrator" refers to New Mountain Guardian's and NMG LLC's administrator, New Mountain Guardian Administration, L.L.C.; and



•

"New Mountain" refers to the affiliated companies of New Mountain Capital, L.L.C.

          In connection with this offering, a series of formation transactions will be undertaken such that following this offering NMG LLC will own all of the existing assets, and will have assumed all of the existing liabilities, of the Guardian Entities. Except where the context suggests otherwise, references to the "Company", "we", "us" and "our" refer to New Mountain Guardian together with NMG LLC, including the combined operations of the Guardian Entities prior to and after the completion of the formation transactions.

The Company

          New Mountain Guardian will be a holding company with no direct operations of its own, and its only business and sole asset will be its ownership of common membership units of NMG LLC, the operating company for our business. NMG LLC will be an externally managed finance company, which will own all of the existing assets, and will have assumed all of the existing liabilities, of the Guardian Entities following this offering. Following the completion of this offering and based on the mid-point of the range set forth on the cover of this prospectus, New Mountain Guardian will own approximately         % and Guardian AIV will indirectly own through Guardian AIV Holdings approximately         % of the common membership units of NMG LLC and Guardian Partners will own approximately         % of New Mountain Guardian's outstanding common stock, assuming no exercise of the underwriters' option to purchase additional shares.

          Our investment strategy, developed by the Investment Advisor, is to invest through NMG LLC primarily in the debt of companies that the Investment Advisor believes are high quality, defensive growth companies, which are defined as generally exhibiting the following characteristics: (i) sustainable secular growth drivers, (ii) high barriers to competitive entry, (iii) high free cash flow after capital expenditure and working capital needs, (iv) high returns on assets and (v) opportunities

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for niche market dominance. The Investment Advisor, through its relationship with New Mountain, already has access to proprietary research and operating insights into many of the companies and industries that meet this template.

          NMG LLC will be externally managed by New Mountain Guardian Advisors, a wholly-owned subsidiary of New Mountain, a private equity firm with a track record of investing in the middle market and with assets under management (which includes amounts committed, not all of which have been drawn down and invested to date) totaling more than $8.5 billion as of March 31, 2010. New Mountain focuses on investing in high quality, defensive growth companies across its private equity, public equity and credit investment vehicles. NMG LLC was formed as a subsidiary of Guardian AIV by New Mountain in October 2008. Guardian AIV was formed through an allocation of approximately $300 million of the $5.1 billion of commitments supporting New Mountain Partners III, L.P., or "Fund III", a private equity fund managed by New Mountain, and in February 2009 New Mountain formed a co-investment vehicle, Guardian Partners, comprising $20 million of commitments.

          Since the commencement of the Guardian Entities' operations in October 2008 through March 31, 2010, approximately $353 million has been invested in 34 companies and total realized and unrealized gains and investment income of approximately $153 million have been earned with an average holding period of seven months. Going forward, we intend to target investments that we believe are capable of yielding a total asset level unlevered return of 10% to 15%, which we view to be an attractive risk adjusted return in normal credit markets. There can be no assurance that targeted returns will be achieved on our investments as they are subject to risks, uncertainties and other factors, some of which are beyond our control, including market conditions. See "Risk Factors — Risks Relating to Our Investments".

          The following charts summarize our portfolio mix by industry and type based on the fair value of our investments as of March 31, 2010, as determined by an affiliated investment advisor (rounded to the nearest whole number).

By Industry		By Type of Investment

          As of March 31, 2010, our portfolio had a fair value of approximately $285 million in 26 portfolio companies and had a weighted average Yield to Maturity of approximately 11.5%. For purposes of this prospectus, references to "Yield to Maturity" assume that the investments in our

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portfolio as of a certain date, the "Portfolio Date", are purchased at fair value on that date and held until their respective maturities with no prepayments or losses and are exited at par at maturity. These references also assume that unfunded revolvers remain undrawn. Interest income is assumed to be received quarterly for all debt securities. For floating rate debt securities, the interest rate is calculated by adding the spread to the projected three-month LIBOR at each respective quarter, which is determined based on the forward three-month LIBOR curve per Bloomberg as of the Portfolio Date. This calculation excludes the impact of existing leverage. The actual yield to maturity may be higher or lower due to the future selection of LIBOR contracts by the individual companies in our portfolio or other factors. Since inception, the Guardian Entities have not experienced any payment defaults or credit losses on our portfolio investments.

          We intend to find and analyze investment opportunities by utilizing the experience of the Investment Advisor's investment professionals. Business and industry due diligence on a targeted investment opportunity is led by a team of investment professionals at the Investment Advisor that generally consists of three to seven individuals, typically based on their relevant company and/or industry specific knowledge, drawn from New Mountain's deep pool of approximately 80 staff members, including approximately 50 investment professionals (including 11 managing directors and 12 senior advisors) as well as nine finance and operational professionals. This is generally the same team structure and due diligence process that is used to underwrite an acquisition of an entire company by New Mountain's private equity fund. Key elements of the team's underwriting process include determining the attractiveness of the target's business model and developing a forecast of its likely operating and financial performance. Team members have diverse backgrounds in investment management, investment banking, consulting and operations. We believe the presence within New Mountain of numerous former CEOs and other senior operating executives, and their active involvement in our underwriting process, combined with New Mountain's experience as a majority stockholder owning and directing a wide range of businesses and overseeing operating companies in the same or related industries, is a key differentiator versus typical debt investment vehicles.

          We expect to primarily target loans to, and invest in, U.S. middle market businesses, a market segment we believe will continue to be underserved by other lenders. We define middle market businesses as those businesses with annual EBITDA between $20 million and $200 million. We expect to make investments through both primary originations and open-market secondary purchases. Our investment objective is to generate current income and capital appreciation through investments in debt securities at all levels of the capital structure, including first and second lien debt, unsecured notes and mezzanine securities, which we refer to as "Target Securities". We believe our focus on investment opportunities with contractual current interest payments should allow us to provide New Mountain Guardian stockholders with consistent dividend distributions and attractive risk adjusted total returns. Our investments may also include equity interests such as preferred stock, common stock, warrants or options received in connection with our debt investments. In some cases, we may invest directly in the equity of private companies. Our investments are intended to generally range in size between $10 million and $50 million, although this investment size may vary proportionately as the size of NMG LLC's capital base changes. From time to time, we may also invest through NMG LLC in other types of investments, which are not our primary focus, to enhance the overall return of the portfolio. These investments may include, but are not limited to, distressed debt and related opportunities.

          NMG LLC is party to a five-year secured credit facility with Wells Fargo Bank, N.A. This credit facility, which matures on October 21, 2014, will survive this offering and provides for borrowings up to $120 million. Unlike many credit facilities for business development companies, the amount available under this credit facility is not subject to reduction as a result of mark to market fluctuations in our portfolio investments. As of March 31, 2010, $67.1 million was outstanding under

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the credit facility. NMG LLC has used borrowings under the credit facility to purchase the senior secured loans and bonds that constitute a portion of our current portfolio. NMG LLC expects to continue to finance our investments using both debt and equity, including proceeds from equity issued by New Mountain Guardian, which would be contributed to NMG LLC.

New Mountain

          New Mountain manages private equity, public equity and debt investments with aggregate assets under management (which includes amounts committed, not all of which have been drawn down and invested to date) totaling more than $8.5 billion as of March 31, 2010.

          New Mountain's first private equity fund, the $770 million New Mountain Partners, L.P., or "Fund I", began its investment period in January 2000. New Mountain's second private equity fund, the $1.6 billion New Mountain Partners II, L.P., or "Fund II", began its investment period in January 2005. New Mountain's third private equity fund, Fund III, with over $5.1 billion of aggregate commitments, began its investment period in August 2007. New Mountain manages public equity portfolios of approximately $1.5 billion through New Mountain Vantage Advisers, L.L.C., which is designed to apply New Mountain's established strengths toward non-control positions in the U.S. public equity markets generally. New Mountain manages its debt portfolio through NMG LLC, and NMG LLC is currently New Mountain's only vehicle focused primarily on investing in the Target Securities.

          New Mountain's mission is to be "best in class" in the new generation of investment managers as measured by returns, control of risk, service to investors and the quality of the businesses in which New Mountain invests. All of New Mountain's efforts emphasize intensive fundamental research and the proactive creation of proprietary investment advantages in carefully selected industry sectors. New Mountain is a generalist firm but has developed particular competitive advantages in what New Mountain believes to be particularly attractive sectors, such as education, healthcare, logistics, business and industrial services, federal IT services, media, software, insurance, consumer products, financial services and technology, infrastructure and energy. New Mountain is focused on systematically establishing expertise in new sectors in which it believes it will have a competitive advantage over time.

          New Mountain is led by 11 managing directors who have over 200 combined years of debt and equity investment experience. The managing directors are supported by New Mountain's team of approximately 40 additional investment professionals (including 12 senior advisors) as well as nine finance and operational professionals.

          New Mountain believes that its funds rank among the highest returning private equity funds of their vintage years with Fund I (2000 vintage year) ranking in the second quartile, Fund II (2005 vintage year) ranking in the first quartile and Fund III (2007 vintage year) ranking in the second quartile of the applicable vintage years, based on reports by Cambridge Associates, LLC and Ventures Economics. This data is based on sample sizes from Cambridge Associates, LLC of 53, 45, and 44 funds and from Venture Economics of 44, 19 and 13 funds for the respective vintage years. In addition, in 2004 and 2007, New Mountain was named "North American Mid-Market Firm of the Year" by Private Equity International. New Mountain has also consistently been named a finalist for "Buyout Firm of the Year" by Buyouts Magazine, having been named one of four finalists for 2009 and 2008 and one of five finalists in 2007. To date, New Mountain has never experienced a bankruptcy of any of its portfolio companies in its private equity efforts or efforts with respect to the Guardian Entities' business.

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New Mountain Guardian Advisors

          New Mountain Guardian will be a holding company with no direct operations of its own, and its only business and sole asset will be its ownership of common membership units of NMG LLC. NMG LLC will be externally managed and advised by the Investment Advisor, New Mountain Guardian Advisors, a wholly-owned subsidiary of New Mountain. New Mountain Guardian Advisors will manage NMG LLC's day-to-day operations and provide it with investment advisory and management services. In particular, New Mountain Guardian Advisors will be responsible for identifying attractive investment opportunities, conducting research and due diligence on prospective investments, structuring our investments and monitoring and servicing our investments. Neither New Mountain Guardian nor NMG LLC currently has or will have any employees. The Investment Advisor is supported by approximately 80 New Mountain staff members, including approximately 50 investment professionals (including 11 managing directors and 12 senior advisors) as well as nine finance and operational professionals. These individuals will allocate a portion of their time in support of the Investment Advisor based on their particular expertise as it relates to a potential investment opportunity.

          The Investment Advisor has an investment committee comprised of five members, including Steven Klinsky, Robert Hamwee, Adam Collins, Douglas Londal and Alok Singh. The investment committee will be responsible for approving all of our investments above $5 million. The investment committee will also monitor investments in our portfolio and approve all asset dispositions above $5 million. Investments and dispositions below $5 million may be approved by NMG LLC's Chief Executive Officer. These approval thresholds may change over time. We expect to benefit from the extensive and varied relevant experience of the investment professionals serving on the Investment Advisor's investment committee, which includes expertise in private equity, primary and secondary leveraged credit, private mezzanine finance and distressed debt.

Recent Developments

Estimated Net Asset Value

          New Mountain Guardian's                , 2010 unaudited net asset value per share is estimated to be $             on an as adjusted basis reflecting the formation transactions and its expected         % ownership in NMG LLC (based on the mid-point of the range set forth on the cover of this prospectus). On                , 2010, NMG LLC's board of directors approved the fair value of our portfolio investments as of                 , 2010 in accordance with NMG LLC's valuation policy and estimated NMG LLC's unaudited net asset value per unit to be $             . NMG LLC's                , 2010 net asset value estimate is based on this board-approved fair value of our portfolio investments as well as other factors, including expected investment income earned on the portfolio. The                          in net asset value from March 31, 2010 to                , 2010 is primarily due to additional purchases and sales of portfolio investments since March 31, 2010,                          of our portfolio investments and NMG LLC's retained investment income. See "Determination of Net Asset Value".

Distributions/Contributions

          For the period from March 31, 2010, to                , 2010, the Guardian Entities received contributions of $        million and made distributions of $        million to the partners of the Guardian Entities.

          New Mountain Guardian's first quarterly distribution, which it expects will be payable in                          2010, is expected to be between $             and $             per share. The actual amount of such distribution, if any, remains subject to approval by New Mountain Guardian's board of directors, and there can be no assurance that any distribution paid will fall within such range. In

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addition, because New Mountain Guardian will be a holding company, it will only be able to pay distributions on its common stock from distributions received from NMG LLC. NMG LLC intends to make distributions to its members that will be sufficient to enable New Mountain Guardian to pay quarterly distributions to its stockholders and to obtain and maintain its status as a regulated investment company, or "RIC", under Subchapter M of the Internal Revenue Code of 1986, as amended (the "Code"). New Mountain Guardian intends to distribute to its stockholders substantially all of its annual taxable income, except that it may retain certain net capital gains for reinvestment in common membership units of NMG LLC.

Recent Portfolio Activity

          From March 31, 2010 to June 30, 2010, the Guardian Entities purchased seven investments in six portfolio companies, totaling approximately $53.6 million and sold seven investments in seven portfolio companies, totaling approximately $27.2 million.

          Set forth below are the purchases and sales between March 31, 2010 and June 30, 2010:

Purchases

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Sales

          After giving effect to the purchases and sales between March 31, 2010 and June 30, 2010 above, our pro forma weighted average Yield to Maturity as of June 30, 2010 would have been 11.8% consisting of: (1) 6.1% cash interest based on LIBOR as of June 30, 2010, (2) an additional 0.9% representing the impact of using the forward three-month LIBOR curve on an asset by asset basis, (3) 1.7% current PIK interest and (4) 3.1% accretion of market discount.

          In addition, in May 2010, NMG LLC's $20.0 million undrawn bridge commitment to an affiliate of SkillSoft Public Limited Company was reduced to zero as a result of the permanent high yield financing secured by its affiliate, SSI Investments II Limited, noted above in which NMG LLC acquired approximately $7.0 million of the permanent financing. In June 2010, NMG LLC acquired a $15.0 million undrawn bridge commitment to inVentiv Health, Inc.

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Competitive Advantages

          We believe that we have the following competitive advantages over other capital providers to middle market companies:

Proven and Differentiated Investment Style With Areas of Deep Industry Knowledge

          In making its investment decisions, the Investment Advisor intends to apply New Mountain's long-standing, consistent investment approach that has been in place since its founding more than 10 years ago. We expect to focus on non-distressed companies in less well followed defensive growth niches of the middle market space where we believe few debt funds have built equivalent research and operational size and scale. The Investment Advisor has a particular emphasis on middle market companies where it believes research scale is often most difficult to achieve, debt financing terms may be most attractive and debt market opportunities may be greatest.

          We expect to benefit directly from New Mountain's private equity investment strategy that seeks to identify attractive investment sectors from the top down and then works to become a well positioned investor in these sectors. New Mountain focuses on companies and end markets with sustainable strengths in all economic cycles, particularly ones that are defensive in nature, that are non-cyclical and can maintain pricing power in the midst of a recessionary and/or inflationary environment. New Mountain focuses on companies within sectors in which it has significant expertise (examples include federal services, software, education, niche healthcare, business services, energy and logistics) while typically avoiding investments in companies with end markets that are highly cyclical, face secular headwinds, are overly-dependent on consumer demand or are commodity-like in nature.

          In making its investment decisions, the Investment Advisor has adopted the approach of New Mountain, which is based on three primary investment principles:

1.

A generalist approach, combined with proactive pursuit of the highest quality opportunities within carefully selected industries, identified via an intensive and structured ongoing research process;



2.

Emphasis on strong downside protection and strict risk controls; and



3.

Continued search for superior risk adjusted returns, combined with timely, intelligent exits and outstanding return performance.

Established Team and Platform

          The Investment Advisor will be supported by an experienced team of approximately 80 New Mountain staff members, including approximately 50 investment professionals (including 11 managing directors and 12 senior advisors) as well as nine finance and operational professionals, drawn from the nation's leading private equity, public equity, debt investment, consulting and accounting firms, including senior-level corporate and operating executives. The Investment Advisor's investment professionals are actively involved in the underwriting of debt investments and are responsible for the diligence and monitoring of the credits. We believe these investment professionals provide the Investment Advisor with a competitive advantage in identifying, investing in and monitoring our investments. The Investment Advisor also has access to teams of operating managers at New Mountain's private equity portfolio companies, consultants on retainer, legal and accounting teams, a management advisory board, directors at portfolio companies and others. We believe the quality and depth of the Investment Advisor's investment professionals distinguishes us from other debt investment funds of similar target investment size.

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          Many of the debt investments that we have made to date have been in the same companies with which New Mountain has already conducted months of intensive acquisition due diligence related to potential private equity investments. We believe that private equity underwriting due diligence is usually more robust than typical due diligence for loan underwriting. In its underwriting of debt investments, the Investment Advisor is able to utilize the research and hands-on operating experience that New Mountain's private equity underwriting teams possess regarding the individual companies and industries. Additionally, the Investment Advisor is also able to utilize its relationships with operating management teams and other private equity sponsors. We believe this will differentiate us from many of our competitors.

Experienced Management Team

          The Investment Advisor's team members have extensive experience in the leveraged lending space. For example, Steven Klinsky, New Mountain's Founder and Chief Executive Officer, was a general partner of the manager of debt and equity funds, totaling multiple billions of dollars at Forstmann Little & Co. in the 1980s and 1990s. He was also a co-founder of Goldman, Sachs & Co.'s Leverage Buyout Group in the period from 1981 to 1984. Robert Hamwee, Managing Director of New Mountain, was formerly President of GSC Group, Inc., or "GSC", which oversaw $22 billion in debt funds, was the portfolio manager of GSC's distressed debt funds and led the development of GSC's CLOs. Douglas Londal, Managing Director of New Mountain, was previously co-head of Goldman, Sachs & Co.'s U.S. mezzanine debt team. Alok Singh, Managing Director of New Mountain, has extensive experience structuring debt products as a long-time partner at Bankers Trust Company.

Significant Sourcing Capabilities and Relationships

          We believe the Investment Advisor's ability to source attractive investment opportunities is greatly aided by both New Mountain's historical and current reviews of private equity opportunities in the business segments we target. To date, a significant majority of the investments we have made through NMG LLC are in the debt of companies and industry sectors we first identified and reviewed in connection with New Mountain's private equity efforts, and the majority of our current pipeline reflects this as well. Furthermore, the Investment Advisor's investment professionals have deep and longstanding relationships in both the private equity sponsor community and the lending/agenting community which they have and will continue to utilize to generate investment opportunities.

Risk Management through Various Cycles

          New Mountain has emphasized tight control of risk since its inception and long before the recent global financial distress began. To date, New Mountain has never experienced a bankruptcy of any of its portfolio companies in its private equity efforts or efforts with respect to the Guardian Entities' business. The Investment Advisor will seek to emphasize tight control of risk with our investments in several important ways, consistent with New Mountain's historical approach. In particular, the Investment Advisor intends to:

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Emphasize the origination of debt in companies that the Investment Advisor believes are high quality, defensive growth companies, which are less likely to be dependent on macro-economic cycles;



•

Target investments in companies that are preeminent market leaders in their own industries, and when possible, investments in companies that have strong management teams whose skills are difficult for competitors to acquire or reproduce; and



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Emphasize capital structure seniority in the Investment Advisor's underwriting process.

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Access to Non Mark to Market, Seasoned Leverage Facility

          We believe NMG LLC's existing credit facility provides us with a substantial amount of capital for deployment into new investment opportunities. In addition, unlike many credit facilities for business development companies, the amount available under the credit facility is not subject to reduction as a result of mark to market fluctuations in our portfolio investments. Since October 2009, leverage has been used to increase return on equity, and NMG LLC intends to continue to use leverage after the completion of this offering, subject to the restrictions on leverage under the Investment Company Act of 1940, or the "1940 Act". The credit facility, pursuant to which NMG LLC is able to borrow up to $120 million, matures on October 21, 2014.

Market Opportunity

          We believe that the size of the market for Target Securities, coupled with the demands of middle market companies for flexible sources of capital at competitive terms and rates, create an attractive investment environment for us.

•

The leverage finance market has a high level of financing needs over the next several years due to significant bank debt maturities.  We believe that the large dollar volume of loans that need to be refinanced will present attractive opportunities to invest capital in a manner consistent with our stated objectives.

Outstanding Loans by Year of Maturity

		Source: Standard & Poor's LCD.

•

Middle market companies continue to face difficulties in accessing the capital markets.  We believe opportunities to serve the middle market will continue to exist. While many middle market companies were formerly able to raise funds by issuing high-yield bonds, we believe this approach to financing has become more difficult in recent years as institutional investors have sought to invest in larger, more liquid offerings. In addition, many private finance companies and hedge funds have reduced their middle market lending activities due to decreased availability of financing.



•

Consolidation among commercial banks has reduced the focus on middle market lending.  We believe that many traditional bank lenders to middle market businesses have either exited or de-emphasized their service and product offerings in the middle market. These traditional lenders have instead focused on lending and providing other services to large

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corporate clients. We believe this has resulted in fewer key players and the reduced availability of debt capital to the companies we target.

FDIC-Insured Institutions

		Source: FDIC.
		Note: Data as of March 31, 2010.

•

Attractive pricing.  Reduced access to, and availability of, debt capital typically increases the interest rates, or pricing, of loans for middle-market lenders. Recent primary debt transactions in this market typically have included meaningful upfront fees, prepayment protections and, in some cases, warrants to purchase common stock, all of which should enhance the profitability of new loans to lenders.

Source: Standard & Poor's LCD and S&P/LSTA Leveraged Loan Index.		Source: Standard & Poor's LCD and S&P/LSTA Leveraged Loan Index.

•

Conservative deal structures.  As a result of the credit crisis, many lenders are requiring larger equity contributions from financial sponsors. Larger equity contributions create an enhanced margin of safety for lenders because leverage is a lower percentage of the implied enterprise value of the company.

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Average Equity Contribution to Leveraged Buyouts (1987 – 4Q09)

Source: Standard & Poor's.

Note: Equity includes common equity and preferred stock as well as holding company debt and seller note proceeds downstreamed to the operating company as common equity. Rollover Equity prior to 1996 is not available. There were too few deals in 1991 to form a meaningful sample.

•

Large pool of uninvested private equity capital available for new buyouts.  We expect that private equity firms will continue to pursue acquisitions and will seek to leverage their equity investments with mezzanine loans and/or senior loans provided by companies such as ours.

North American Private Equity Available Capital

Source: Preqin data as of December 31, 2009.

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Our History and Structure

          New Mountain Guardian was incorporated in Delaware on June 29, 2010. Prior to this offering, it did not engage in any activities, except in preparation for this offering, and it had no operations or assets. New Mountain currently owns the only issued and outstanding share of common stock of New Mountain Guardian. NMG LLC was formed as a subsidiary of Guardian AIV by New Mountain in October 2008. Guardian AIV was formed through an allocation of approximately $300 million of the $5.1 billion of commitments supporting Fund III, a private equity fund managed by New Mountain, and in February 2009 New Mountain formed a co-investment vehicle, Guardian Partners, comprising $20 million of commitments.

          The simplified diagram below depicts our current organizational structure prior to the structuring transactions contemplated by this offering:

          In connection with this offering, a series of formation transactions will be undertaken such that, following this offering, NMG LLC will own all of the existing assets, and will have assumed all of the existing liabilities, of the Guardian Entities. As a result of these transactions, Guardian AIV will indirectly own through its wholly-owned subsidiary, Guardian AIV Holdings, common membership units of NMG LLC, and Guardian Partners will own shares of New Mountain Guardian's common stock. New Mountain Guardian will enter into an acquisition agreement, or the "Acquisition Agreement", with NMG LLC, pursuant to which it will purchase from NMG LLC, with the gross proceeds of this offering,                            common membership units of NMG LLC (the number of common membership units will equal the number of shares of New Mountain Guardian's common stock sold in this offering) in connection with the completion of this offering. The per unit purchase price New Mountain Guardian will pay for the common membership units purchased pursuant to the Acquisition Agreement will be equal to the per share offering price at which New Mountain Guardian's common stock is sold pursuant to this offering. After the completion of this offering, New Mountain Guardian will be a holding company with no direct operations of its own, and its

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only business and sole asset will be its ownership of common membership units of NMG LLC. See "Formation Transactions and Related Agreements".

          Based on the mid-point of the range set forth on the cover of this prospectus, New Mountain Guardian will own approximately         % and Guardian AIV will indirectly own through Guardian AIV Holdings approximately         % of the common membership units of NMG LLC and Guardian Partners will own approximately         % of New Mountain Guardian's outstanding common stock, assuming no exercise of the underwriters' option to purchase additional shares. If the underwriters exercise this option to purchase additional shares of New Mountain Guardian's common stock, pursuant to the Acquisition Agreement, immediately thereafter New Mountain Guardian will acquire from NMG LLC an equivalent number of additional common membership units in exchange for the gross proceeds New Mountain Guardian receives upon exercise of the option.

          Prior to this offering, NMG LLC will calculate net asset value per unit of NMG LLC, the "cutoff NAV", as of                          , 2010, the "cutoff date". The cutoff NAV will be determined and approved by NMG LLC's board of directors and will be calculated consistent with its policies for determining net asset value. See "Determination of Net Asset Value". Consistent with these policies, an independent third party valuation firm will provide NMG LLC with valuation assistance with respect to each investment for which market quotations are not available. NMG LLC will accrue interest income and related expenses as of the cutoff date. The cutoff NAV calculation will be comprised of all the investments at fair value plus any interest income accruals, less any expense accruals through the cutoff date. NMG LLC will not accept any contributions from, nor make any distributions to, the Guardian Entities' limited partners from the cutoff date through the date of this offering.

          In addition, certain executives and employees of, and other individuals affiliated with, New Mountain have committed to purchase              shares of New Mountain Guardian's common stock in connection with the consummation of this offering. These shares will be sold at the same offering price paid by investors in this offering, before taking into account the underwriting discounts and commissions, in a private placement transaction exempt from registration under the Securities Act of 1933, as amended, or the Securities Act. We refer to this transaction as the "concurrent private placement".

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          The simplified diagram below depicts our summarized organizational structure immediately after the transactions described in this prospectus (assuming no exercise of the underwriters' option to purchase additional shares):

*

These common membership units are exchangeable into shares of New Mountain Guardian common stock on a one-for-one basis.

Operating and Regulatory Structure

          After the completion of this offering, New Mountain Guardian will be a closed-end, non-diversified management investment company that has elected to be treated as a business development company under the 1940 Act and it will have no material long-term liabilities. New Mountain Guardian's only business and sole asset will be its ownership of common membership units of NMG LLC. As a result, New Mountain Guardian will look to NMG LLC's assets for purposes of satisfying the requirements under the 1940 Act otherwise applicable to New Mountain Guardian. NMG LLC will be an externally managed, closed-end non-diversified management investment company that has elected to be treated as a business development company under the 1940 Act. As a business development company, NMG LLC will be required to maintain an asset coverage ratio, as defined in the 1940 Act, of at least 200%. See "Regulation".

          New Mountain Guardian intends to elect to be treated, and intends to qualify annually, as a RIC under Subchapter M of the Code, commencing with its taxable year ending on December 31, 2010. See "Material Federal Income Tax Considerations". As a RIC, New Mountain Guardian generally will not have to pay corporate-level federal income taxes on any net ordinary income or capital gains that it timely distributes to its stockholders as dividends if it meets certain source-of-income, distribution and asset diversification requirements. NMG LLC intends to make distributions to its members that will be sufficient to enable New Mountain Guardian to pay quarterly distributions to its stockholders and to obtain and maintain its status as a RIC. New Mountain Guardian intends to distribute to its stockholders substantially all of its annual taxable income,

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except that it may retain certain net capital gains for reinvestment in common membership units of NMG LLC.

Risk Factors

          An investment in New Mountain Guardian's common stock involves risk, including the risk of leverage and the risk that our operating policies and strategies may change without prior notice to New Mountain Guardian stockholders or prior stockholder approval. See "Risk Factors" and the other information included in this prospectus for a discussion of factors you should carefully consider before deciding to invest in shares of New Mountain Guardian's common stock. The value of NMG LLC's assets, as well as the market price of New Mountain Guardian's shares, will fluctuate. Our investments may be risky, and you may lose all or part of your investment in New Mountain Guardian. Investing in New Mountain Guardian involves other risks, including the following:

•

We have a limited operating history;



•

We may not replicate the Guardian Entities' historical performance or the historical performance of other entities managed or supported by New Mountain;



•

There will be uncertainty as to the value of our portfolio investments because most of our investments are, and will continue to be, recorded at fair value. In addition, because New Mountain Guardian will be a holding company, its board of directors will have no control over the determinations of fair value of our investments, which will be determined by NMG LLC's board of directors;



•

Our ability to achieve our investment objective depends on key investment personnel of the Investment Advisor. If the Investment Advisor were to lose any of its key investment personnel, our ability to achieve our investment objective could be significantly harmed;



•

New Mountain Guardian, NMG LLC and the Investment Advisor do not have any prior experience managing a business development company or a RIC, which could adversely affect our business;



•

We operate in a highly competitive market for investment opportunities and may not be able to compete effectively;



•

NMG LLC will borrow money, which could magnify the potential for gain or loss on amounts invested in us and increase the risk of investing in us;



•

Regulations governing the operations of business development companies will affect New Mountain Guardian's ability to raise additional equity capital as well as NMG LLC's ability to issue senior securities or borrow for investment purposes, any or all of which could have a negative effect on our investment objectives and strategies;



•

We may experience fluctuations in our annual and quarterly results due to the nature of our business;



•

NMG LLC's board of directors may change our investment objective, operating policies and strategies without prior notice or member approval, the effects of which may be adverse to your interest as a stockholder;



•

New Mountain Guardian will be subject to corporate-level federal income tax on all of its income if it is unable to qualify as a RIC under Subchapter M of the Code, which would have a material adverse effect on its financial performance;



•

New Mountain Guardian may not be able to pay you distributions on its common stock, its distributions to you may not grow over time and a portion of its distributions to you may be a return of capital for federal income tax purposes;



•

Our investments in portfolio companies may be risky, and we could lose all or part of our investment;

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•

The lack of liquidity in our investments may adversely affect our business;



•

Economic recessions or downturns could impair our portfolio companies and harm our operating results;



•

Changes in interest rates may affect NMG LLC's cost of capital and net investment income;



•

New Mountain Guardian will be a holding company with no direct operations of its own, and will depend on distributions from NMG LLC to meet its ongoing obligations;



•

Any future exchange by Guardian AIV Holdings of common membership units of NMG LLC for shares of New Mountain Guardian's common stock would significantly dilute your voting power with respect to the election of New Mountain Guardian directors or other matters that require the approval of New Mountain Guardian stockholders only. In addition, the interests of the partners of Guardian AIV following such exchange by Guardian AIV Holdings may be adverse to your interests as stockholders and could limit your ability to influence the outcome of key transactions, including any change of control;



•

The market price of New Mountain Guardian's common stock may fluctuate significantly;



•

Prior to this offering, there has been no public market for New Mountain Guardian's common stock, and we cannot assure you that the market price of New Mountain Guardian's common stock will not decline following the offering;



•

We have not identified specific investments in which NMG LLC will invest the proceeds of this offering; and



•

Sales of substantial amounts of New Mountain Guardian's common stock in the public market may have an adverse effect on the market price of its common stock.

Company Information

          Our administrative and executive offices are located at 787 7th Avenue, 48th Floor, New York, New York 10019, and our telephone number is (212) 720-0300. We expect to establish a website at http://www.newmountainguardian.com upon completion of this offering. Information contained on our website is not incorporated by reference into this prospectus, and you should not consider information contained on our website to be part of this prospectus.

Presentation of Historical Financial Information and Market Data

Historical Financial Information

          NMG LLC is considered to be New Mountain Guardian's predecessor for accounting purposes and the combined financial statements of New Mountain Guardian Holdings, L.L.C., formerly known as New Mountain Guardian (Leveraged), L.L.C., and New Mountain Guardian Partners, L.P. are NMG LLC's historical combined financial statements. Unless otherwise indicated, historical references contained in this prospectus in "Selected Financial and Other Data", "Capitalization", "Management's Discussion and Analysis of Financial Condition and Results of Operations", "Senior Securities", "Portfolio Companies" and our historical combined financial statements contained elsewhere in this prospectus, relate to NMG LLC.

Market Data

          Statistical and market data used in this prospectus has been obtained from governmental and independent industry sources and publications. We have not independently verified the data obtained from these sources, and we cannot assure you of the accuracy or completeness of the data. Forward-looking information obtained from these sources is subject to the same qualifications and the additional uncertainties regarding the other forward-looking statements contained in this prospectus. See "Special Note Regarding Forward-Looking Statements".

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THE OFFERING

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          Unless otherwise indicated, all information in this prospectus reflects the consummation of the formation transactions described in "Formation Transactions and Related Agreements".

          A nominal amount of shares of New Mountain Guardian's common stock was outstanding prior to the completion of this offering. The number of shares of New Mountain Guardian's common stock to be outstanding after completion of this offering is based on                           shares of New Mountain Guardian's common stock to be sold in this offering and the concurrent private placement at the mid-point of the range set forth on the cover of this prospectus, and except where we state otherwise, the common stock information presented in this prospectus:

•

excludes              shares of New Mountain Guardian's common stock issuable upon exchange of common membership units of NMG LLC held by Guardian AIV Holdings upon exercise of its exchange rights, as described under "Formation Transactions and Related Agreements — Structure-Related Agreements — NMG LLC Agreement"; and



•

assumes no exercise by the underwriters of their option to purchase up to              additional shares of New Mountain Guardian's common stock.

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FEES AND EXPENSES

          The following table is intended to assist you in understanding the costs and expenses that an investor in this offering will bear directly or indirectly. We caution you that some of the percentages indicated in the table below are estimates and may vary. Except where the context suggests otherwise, whenever this prospectus contains a reference to fees or expenses paid by "you", "New Mountain Guardian", "NMG LLC", or "us" or that "we", "New Mountain Guardian", or "NMG LLC" will pay fees or expenses, stockholders will indirectly bear such fees or expenses through New Mountain Guardian's investment in NMG LLC.

Example

          The following example demonstrates the projected dollar amount of total cumulative expenses that would be incurred over various periods with respect to a hypothetical investment in New Mountain Guardian's common stock. In calculating the following expense amounts, we have excluded performance-based incentive fees, assumed that NMG LLC's borrowings and annual expenses would remain at the levels set forth in the table above and assumed that you would pay a sales load of         % (the underwriting discount and commission to be paid by NMG LLC with respect to common stock sold by New Mountain Guardian in this offering).

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          The example and the expenses in the tables above should not be considered a representation of future expenses, and actual expenses may be greater or less than those shown. While the example assumes, as required by the applicable rules of the SEC, a 5% annual return, our performance will vary and may result in a return greater or less than 5%. The incentive fee under the Investment Management Agreement, which, assuming a 5% annual return, would either not be payable or would have an insignificant impact on the expense amounts shown above, is not included in the example. If NMG LLC achieves sufficient returns on our investments, including through the realization of capital gains, to trigger an incentive fee of a material amount, its expenses, and returns to New Mountain Guardian investors, would be higher. In addition, while the example assumes reinvestment of all distributions at net asset value, participants in New Mountain Guardian's dividend reinvestment plan will receive a number of shares of New Mountain Guardian's common stock, determined by dividing the total dollar amount of the distribution payable to a participant by the market price per share of New Mountain Guardian's common stock at the close of trading on the dividend payment date fixed by New Mountain Guardian's board of directors, which may be at, above or below net asset value. See "Dividend Reinvestment Plan" for additional information regarding the dividend reinvestment plan.

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SELECTED FINANCIAL AND OTHER DATA

          The selected combined financial and other data below reflects the combined historical operations of New Mountain Guardian Holdings, L.L.C., formerly known as New Mountain Guardian (Leveraged), L.L.C., and New Mountain Guardian Partners, L.P., the assets of which will be contributed to NMG LLC in connection with the formation transactions. This combined financial and other data is NMG LLC's historical financial and other data. To date, New Mountain Guardian Corporation has had no operations. As described in "Formation Transactions and Related Agreements — Holding Company Structure", following the completion of this offering, New Mountain Guardian will be a holding company with no direct operations of its own, and its only business and sole asset will be its ownership of common membership units of NMG LLC.

          We have derived the selected historical balance sheet information as of December 31, 2008 and 2009 and the selected statement of operations information for the period from October 29, 2008 (inception) through December 31, 2008 and for the year ended December 31, 2009 from our audited combined financial statements included elsewhere in this prospectus. We have derived the selected historical balance sheet information as of March 31, 2010 and the selected statement of operations information for the three months ended March 31, 2009 and 2010 from our unaudited combined financial statements included elsewhere in this prospectus. The unaudited interim combined financial statements include all adjustments (consisting of normal, recurring adjustments) that are, in the opinion of management, necessary for a fair presentation of our financial position.

          Our historical financial information does not reflect the allocation of certain general and administrative costs or other expenses or the impact of management fees that were incurred by affiliates of New Mountain. We expect that, following the completion of this offering, our share of expenses and management fees as a stand-alone company will be higher than those historically incurred by NMG LLC. Accordingly, our historical financial information should not be relied upon as being representative of our financial position or operating results had we operated on a stand-alone basis under similar regulatory constraints, nor are they representative of our financial position or operating results following this offering. In addition, following the completion of this offering, New Mountain Guardian will own approximately         % of the common membership units of NMG LLC. Depending on New Mountain Guardian's ownership interest in NMG LLC, New Mountain Guardian's results of operations may not be consolidated with NMG LLC's results of operations in future periods. As a result, our historical and future financial information may not be representative of New Mountain Guardian's financial information in future periods.

          The financial and other information below should be read in conjunction with "Management's Discussion and Analysis of Financial Condition and Results of Operations", "Senior Securities" and

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our combined financial statements and related notes, which are included elsewhere in this prospectus.

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RISK FACTORS

          Investing in New Mountain Guardian's common stock involves a number of significant risks. In addition to the other information contained in this prospectus, you should consider carefully the following information before making an investment in New Mountain Guardian's common stock. The risks set out below are not the only risks we face. Additional risks and uncertainties not presently known to us or not presently deemed material by us might also impair our operations and performance. If any of the following events occur, our business, financial condition and results of operations could be materially and adversely affected. In such case, our net asset value and the trading price of New Mountain Guardian's common stock could decline, and you may lose all or part of your investment.

Risks Relating to Our Business

We have a limited operating history.

          New Mountain Guardian is a newly-formed entity and NMG LLC commenced operations in October 2008. Following this offering, NMG LLC will own all of the existing assets, and will have assumed all of the existing liabilities, of the Guardian Entities. New Mountain Guardian will be a holding company with no direct operations of its own, and its only business and sole asset will be its ownership of common membership units of NMG LLC. As a result, we will be subject to many of the business risks and uncertainties associated with any new business, including the risk that we will not achieve our investment objective and that, as a result, the value of New Mountain Guardian's common stock could decline substantially.

We may not replicate the Guardian Entities' historical performance or the historical performance of other entities managed or supported by New Mountain.

          We do not expect that we will replicate the Guardian Entities' historical performance or the historical performance of New Mountain's investments, and our investment returns may be substantially lower than the returns achieved by the Guardian Entities. Although the Guardian Entities commenced operations during otherwise unfavorable economic conditions, this was a favorable environment in which to conduct our business in light of our investment objectives and strategy. In addition, our investment strategies may differ from those of New Mountain or its affiliates. New Mountain Guardian and NMG LLC, as business development companies, and New Mountain Guardian, as a RIC, and NMG LLC as a result of New Mountain Guardian being a RIC, are subject to certain regulatory restrictions that do not apply to New Mountain or its affiliates.

          NMG LLC will generally not be permitted to invest in any private company in which New Mountain or any of its affiliates holds an existing investment, except to the extent permitted by the 1940 Act. This may adversely affect the pace at which NMG LLC makes investments. Moreover, we expect NMG LLC will operate with a different leverage profile than the Guardian Entities. Furthermore, none of the prior results were from public reporting companies, and all or a portion of these results were achieved in particularly favorable market conditions for our investment strategy which may never be repeated. Finally, we can offer no assurance that the Investment Advisor will be able to continue to implement our investment objective with the same degree of success as it has had in the past.

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There will be uncertainty as to the value of our portfolio investments because most of our investments are, and will continue to be, recorded at fair value. In addition, because New Mountain Guardian will be a holding company, its board of directors will have no control over the determinations of fair value of our investments, which will be determined by NMG LLC's board of directors.

          Some of our investments are and will be in the form of securities or loans that are not publicly traded. The fair value of these investments may not be readily determinable. Under the 1940 Act, NMG LLC is required to carry our portfolio investments at market value or, if there is no readily available market value, at fair value as determined in good faith by its board of directors, including to reflect significant events affecting the value of our securities. NMG LLC will value our investments for which it does not have readily available market quotations quarterly, or more frequently as circumstances require, at fair value as determined in good faith by its board of directors in accordance with its valuation policy, which is at all times consistent with generally accepted accounting principles. NMG LLC's board of directors expects to utilize the services of one or more independent third-party valuation firms to aid it in determining the fair value with respect to its material unquoted assets in any given quarter. We expect that inputs into the determination of fair value of these investments may require significant management judgment or estimation. Even if observable market data are available, such information may be the result of consensus pricing information or broker quotes, which include a disclaimer that the broker would not be held to such a price in an actual transaction. The non-binding nature of consensus pricing and/or quotes accompanied by disclaimers materially reduces the reliability of such information. The types of factors that the board of directors may take into account in determining the fair value of our investments generally include, as appropriate: available market data, including relevant and applicable market trading and transaction comparables, applicable market yields and multiples, security covenants, call protection provisions, information rights, the nature and realizable value of any collateral, the portfolio company's ability to make payments, its earnings and discounted cash flows and the markets in which it does business, comparisons of financial ratios of peer companies that are public, comparable merger and acquisition transactions and the principal market and enterprise values. Because these valuations, and particularly valuations of private securities and private companies, are inherently uncertain, may fluctuate over short periods of time and may be based on estimates, NMG LLC's determinations of fair value may differ materially from the values that would have been used if a ready market for these securities existed. Due to this uncertainty, NMG LLC's fair value determinations may cause its net asset value and, consequently, New Mountain Guardian's net asset value on any given date to materially understate or overstate the value that NMG LLC may ultimately realize upon the sale of one or more of our investments. Because New Mountain Guardian will be a holding company and its only business and sole asset will be its ownership of common membership units of NMG LLC, New Mountain Guardian's net asset value will be based on NMG LLC's valuation and its percentage interest in NMG LLC. New Mountain Guardian's board of directors will have no control over the determinations of fair value by NMG LLC's board of directors. Although NMG LLC's initial board of directors will be comprised of the same individuals as New Mountain Guardian's board of directors, there can be no assurances that NMG LLC's board composition will remain the same as New Mountain Guardian's following the completion of this offering. As a result, the value of your investment in New Mountain Guardian could be similarly understated or overstated based on NMG LLC's fair value determinations. In addition, investors purchasing New Mountain Guardian's common stock based on an overstated net asset value would pay a higher price than the realizable value of our investments might warrant.

          NMG LLC will adjust quarterly the valuation of our portfolio to reflect its board of directors' determination of the fair value of each investment in our portfolio. Any changes in fair value will be recorded in NMG LLC's statement of operations as net change in unrealized appreciation or depreciation.

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Our ability to achieve our investment objective depends on key investment personnel of the Investment Advisor. If the Investment Advisor were to lose any of its key investment personnel, our ability to achieve our investment objective could be significantly harmed.

          We will depend on the investment judgment, skill and relationships of the investment professionals of the Investment Advisor, particularly Steven Klinsky and Robert Hamwee, as well as other key personnel to identify, evaluate, negotiate, structure, execute, monitor and service our investments. The Investment Advisor is an affiliate of New Mountain and will be supported by New Mountain's team of approximately 80 staff members, including approximately 50 investment professionals (including 11 managing directors and 12 senior advisors) as well as nine finance and operational professionals and other resources of New Mountain and its affiliates to fulfill its obligations to NMG LLC under the Investment Management Agreement. The Investment Advisor may also depend upon New Mountain to obtain access to investment opportunities originated by the professionals of New Mountain and its affiliates. Our future success will depend to a significant extent on the continued service and coordination of the key investment personnel of the Investment Advisor. The departure of any of these individuals could have a material adverse effect on our ability to achieve our investment objective.

          The Investment Advisor's investment committee, which provides oversight over our investment activities, is provided by the Investment Advisor under the Investment Management Agreement. New Mountain Guardian Advisors' investment committee currently consists of five members. The loss of any member of the Investment Advisor's investment committee or of other senior professionals of the Investment Advisor and its affiliates without suitable replacement could limit our ability to achieve our investment objective and operate as we anticipate. This could have a material adverse effect on our financial condition, results of operation and cash flows. To achieve our investment objective, the Investment Advisor may need to hire, train, supervise and manage new investment professionals to participate in our investment selection and monitoring process. If the Investment Advisor is unable to find investment professionals or do so in a timely manner, our business, financial condition and results of operations could be adversely affected.

New Mountain Guardian, NMG LLC and the Investment Advisor do not have any prior experience managing a business development company or a RIC, which could adversely affect our business.

          New Mountain Guardian, NMG LLC and the Investment Advisor have not previously managed a business development company or a RIC. The 1940 Act and the Code impose numerous constraints on the operations of business development companies and RICs that do not apply to the other investment vehicles previously managed by the investment professionals of the Investment Advisor. For example, under the 1940 Act, business development companies are required to invest at least 70% of their total assets primarily in securities of qualifying U.S. private or thinly traded companies, cash, cash equivalents, U.S. government securities and other high quality debt investments that mature in one year or less. See "Regulation". Moreover, qualification for taxation as a RIC under subchapter M of the Code requires satisfaction of source-of-income, asset diversification and annual distribution requirements. New Mountain Guardian will have no assets other than its ownership of common membership units of NMG LLC and will have no material long-term liabilities. As a result, New Mountain Guardian will look to NMG LLC's assets and income for purposes of satisfying the requirements under the 1940 Act applicable to business development companies and RICs. The failure to comply with these provisions in a timely manner could prevent New Mountain Guardian and NMG LLC from qualifying as business development companies or New Mountain Guardian from qualifying as a RIC and could force us to pay unexpected taxes and penalties, which would have a material adverse effect on our performance. The Investment Advisor's lack of experience in managing a portfolio of assets under the constraints applicable to

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business development companies and RICs may hinder its ability to take advantage of attractive investment opportunities and, as a result, achieve our investment objective. If NMG LLC fails to maintain its status as a business development company or operate in a manner consistent with New Mountain Guardian's status as a RIC, its operating flexibility could be significantly reduced and New Mountain Guardian may be unable to maintain its status as a business development company or a RIC.

We operate in a highly competitive market for investment opportunities and may not be able to compete effectively.

          We compete for investments with other business development companies and investment funds (including private equity funds), as well as traditional financial services companies such as commercial banks and other sources of funding. Many of our competitors are substantially larger and have considerably greater financial, technical and marketing resources than we do. For example, some competitors may have a lower cost of capital and access to funding sources that are not available to us. In addition, some of our competitors may have higher risk tolerances or different risk assessments than we have. Furthermore, many of our competitors have greater experience operating under, or are not subject to, the regulatory restrictions that the 1940 Act will impose on New Mountain Guardian and NMG LLC as business development companies or the source-of-income, asset diversification and distribution requirements that New Mountain Guardian must satisfy to obtain and maintain its RIC status. These characteristics could allow our competitors to consider a wider variety of investments, establish more relationships and offer better pricing and more flexible structuring than we are able to do.

          We may lose investment opportunities if we do not match our competitors' pricing, terms and structure. With respect to the investments we make, we will not seek to compete based primarily on the interest rates we will offer, and we believe that some of our competitors may make loans with interest rates that will be lower than the rates we offer. In the secondary market for acquiring existing loans, we expect to compete generally on the basis of pricing terms. If we match our competitors' pricing, terms and structure, we may experience decreased net interest income, lower yields and increased risk of credit loss. If we are forced to match our competitors' pricing, terms and structure, we may not be able to achieve acceptable returns on our investments or may bear substantial risk of capital loss. Part of our competitive advantage stems from the fact that we believe the market for middle-market lending is underserved by traditional bank lenders and other financial sources. A significant increase in the number and/or the size of our competitors in this target market could force us to accept less attractive investment terms. We may also compete for investment opportunities with accounts managed by the Investment Advisor or its affiliates. Although the Investment Advisor will allocate opportunities in accordance with its policies and procedures, allocations to such other accounts will reduce the amount and frequency of opportunities available to us and may not be in the best interests of us and, consequently, New Mountain Guardian's stockholders. Moreover, the performance of investment opportunities will not be known at the time of allocation. See "— The Investment Advisor has significant potential conflicts of interest with New Mountain Guardian and NMG LLC and, consequently, your interests as stockholders which could adversely impact our investment returns" and "Certain Relationships and Related Transactions". If we are not able to compete effectively, our business, financial condition and results of operations will be adversely affected. Because of this competition, there can be no assurance that we will be able to identify and take advantage of attractive investment opportunities that we identify or that we will be able to fully invest our available capital.

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Our business, results of operations and financial condition will depend on NMG LLC's ability to manage future growth effectively.

          Our ability to achieve our investment objective and to grow depends on the Investment Advisor's ability to identify, invest in and monitor companies that meet our investment criteria. Accomplishing this result on a cost-effective basis is largely a function of the Investment Advisor's structuring of the investment process, its ability to provide competent, attentive and efficient services to NMG LLC and its ability to access financing on acceptable terms. The Investment Advisor has substantial responsibilities under the Investment Management Agreement and may also be called upon to provide managerial assistance to our portfolio companies. These demands on the time of the Investment Advisor and its investment professionals may distract them or slow NMG LLC's rate of investment. In order to grow, NMG LLC and the Investment Advisor may need to retain, train, supervise and manage new investment professionals. However, these investment professionals may not be able to contribute effectively to the work of the Investment Advisor. If we are unable to manage our future growth effectively, our business, results of operations and financial condition could be materially adversely affected.

The incentive fee may induce the Investment Advisor to make speculative investments.

          The incentive fee payable to the Investment Advisor may create an incentive for the Investment Advisor to pursue investments that are risky or more speculative than would be the case in the absence of such compensation arrangement, which could result in higher investment losses, particularly during cyclical economic downturns. The incentive fee payable to the Investment Advisor is calculated based on a percentage of NMG LLC's return on investment capital. This may encourage the Investment Advisor to use leverage to increase the return on our investments. In addition, because the base management fee is payable based upon NMG LLC's gross assets, which includes any borrowings for investment purposes, but excludes cash and cash equivalents for investment purposes, the Investment Advisor may be further encouraged to use leverage to make additional investments. Under certain circumstances, the use of leverage may increase the likelihood of default, which would impair the value of New Mountain Guardian's common membership units of NMG LLC and, consequently, the value of New Mountain Guardian's common stock.

          The incentive fee payable to the Investment Advisor also may create an incentive for the Investment Advisor to invest in instruments that have a deferred interest feature, even if such deferred payments would not provide the cash necessary for NMG LLC to make distributions to New Mountain Guardian that enable New Mountain Guardian to pay current distributions to its stockholders. Under these investments, NMG LLC would accrue the interest over the life of the investment but would not receive the cash income from the investment until the end of the investment's term, if at all. NMG LLC's net investment income used to calculate the income portion of the incentive fee, however, includes accrued interest. Thus, a portion of the incentive fee would be based on income that NMG LLC has not yet received in cash and may never receive in cash if the portfolio company is unable to satisfy such interest payment obligations. In addition, the "catch-up" portion of the incentive fee may encourage the Investment Advisor to accelerate or defer interest payable by portfolio companies from one calendar quarter to another, potentially resulting in fluctuations in timing and dividend amounts.

NMG LLC will borrow money, which could magnify the potential for gain or loss on amounts invested in us and increase the risk of investing in us.

          NMG LLC intends to borrow money as part of our business plan. Borrowings, also known as leverage, magnify the potential for gain or loss on invested equity capital and may, consequently,

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increase the risk of investing in us. We expect NMG LLC to continue to use leverage to finance our investments, through senior securities issued by banks and other lenders. Lenders of these senior securities will have fixed dollar claims on NMG LLC's assets that will be superior to New Mountain Guardian's claim as a member of NMG LLC, and, consequently, superior to claims of New Mountain Guardian's common stockholders. If the value of NMG LLC's assets decreases, leveraging would cause its net asset value and, consequently, New Mountain Guardian's net asset value, to decline more sharply than it otherwise would have had it not leveraged. Similarly, any decrease in NMG LLC's income would cause its net income and consequently New Mountain Guardian's net income to decline more sharply than it would have had it not borrowed. Such a decline could adversely affect NMG LLC's ability to make distributions to its members and, consequently, New Mountain Guardian's ability to make common stock dividend payments. In addition, because our investments may be illiquid, NMG LLC may be unable to dispose of them or to do so at a favorable price in the event it needs to do so if it is unable to refinance any indebtedness upon maturity and, as a result, we may suffer losses. Leverage is generally considered a speculative investment technique.

          NMG LLC's ability to service any debt that it incurs will depend largely on its financial performance and will be subject to prevailing economic conditions and competitive pressures. Moreover, as the Investment Advisor's management fee will be payable to the Investment Advisor based on gross assets, including those assets acquired through the use of leverage, the Investment Advisor may have a financial incentive to incur leverage which may not be consistent with New Mountain Guardian's interests and the interests of its common stockholder. In addition, holders of New Mountain Guardian's common stock will, indirectly, bear the burden of any increase in NMG LLC's expenses as a result of leverage, including any increase in the management fee payable to the Investment Advisor.

          At March 31, 2010, NMG LLC had $67.1 million of indebtedness outstanding, which had an effective annual interest rate of 3.2%. In order for NMG LLC to cover these annualized interest payments on indebtedness, it must achieve annual returns on its assets of at least 0.7% based on the amount of its assets at March 31, 2010.

          Illustration.    The following table illustrates the effect of leverage on returns from an investment in New Mountain Guardian's common stock assuming various annual returns, net of expenses. The calculations in the table below are hypothetical. Actual returns may be higher or lower than those appearing below and will also depend on New Mountain Guardian's ownership interest in NMG LLC. The calculation assumes (i) $324.1 million in total assets, (ii) a weighted average cost of borrowings of 3.2%, (iii) $67.1 million in debt outstanding and (iv) $251.1 million in stockholders' equity.

Assumed Return on Our Portfolio
(net of expenses)

New Mountain Guardian and NMG LLC may need to raise additional capital to grow because New Mountain Guardian must distribute most of its income.

          All of the proceeds from this offering and the concurrent private placement will be contributed to NMG LLC in exchange for New Mountain Guardian's acquisition of common membership units of NMG LLC. New Mountain Guardian and NMG LLC may need additional capital to fund new investments and grow our portfolio of investments once NMG LLC has fully invested these

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proceeds. New Mountain Guardian may access the capital markets periodically to issue equity securities, which would in turn increase the equity capital available to NMG LLC. In addition, NMG LLC may also issue debt securities or borrow from financial institutions in order to obtain such additional capital. Under the 1940 Act, New Mountain Guardian is not permitted to own any other securities other than its common membership units of NMG LLC. As a result, any proceeds from offerings by New Mountain Guardian of equity securities would be contributed to NMG LLC. Unfavorable economic conditions could increase New Mountain Guardian's and NMG LLC's funding costs, limit their access to the capital markets or result in a decision by lenders not to extend credit to NMG LLC. A reduction in the availability of new capital could limit our ability to grow. In addition, New Mountain Guardian will be required to distribute at least 90% of its net ordinary income and net short-term capital gains in excess of net long-term capital losses, if any, to its stockholders to obtain and maintain its RIC status. As a result, these earnings will not be available to fund new investments. If New Mountain Guardian or NMG LLC is unable to access the capital markets or if NMG LLC is unable to borrow from financial institutions, NMG LLC may be unable to grow our business and execute our business strategy fully and our earnings, if any, could decrease which could have an adverse effect on the value of New Mountain Guardian's securities.

If NMG LLC is unable to comply with the covenants or restrictions in the existing credit facility, our business could be materially adversely affected.

          The credit facility includes covenants that, among other things, restrict NMG LLC's ability to dispose of assets, incur additional indebtedness, make restricted payments, create liens on assets, make investments, make acquisitions and engage in mergers or consolidations. The credit facility also includes change of control provisions that accelerate the indebtedness under the facility in the event of certain change of control events. In addition, the credit facility also requires NMG LLC to comply with various financial covenants. See "Management's Discussion and Analysis of Financial Condition and Results of Operations — Liquidity and Capital Resources". Complying with these restrictions may prevent NMG LLC from taking actions that we believe would help it to grow our business or are otherwise consistent with our investment objective. These restrictions could also limit NMG LLC's ability to plan for or react to market conditions or meet extraordinary capital needs or otherwise restrict corporate activities. See "Management's Discussion and Analysis of Financial Condition and Results of Operations — Liquidity and Capital Resources" for additional information regarding NMG LLC's credit arrangements. In addition, the restrictions contained in the credit facility could limit NMG LLC's ability to make distributions to its members in certain circumstances which could result in New Mountain Guardian failing to qualify as a RIC and thus becoming subject to corporate-level federal income tax (and any applicable state and local taxes).

          The breach of any of the covenants or restrictions unless cured within the applicable grace period, would result in a default under the credit facility that would permit the lender to declare all amounts outstanding to be due and payable. In such an event, NMG LLC may not have sufficient assets to repay such indebtedness. As a result, any default could have serious consequences to our financial condition. An event of default or an acceleration under the credit facility could also cause a cross-default or cross-acceleration of another debt instrument or contractual obligation, which would adversely impact NMG LLC's liquidity. NMG LLC may not be granted waivers or amendments to the credit facility if for any reason it is unable to comply with it, and NMG LLC may not be able to refinance the credit facility on terms acceptable to it, or at all.

NMG LLC may enter into reverse repurchase agreements, which are another form of leverage.

          NMG LLC may enter into reverse repurchase agreements as part of its management of our temporary investment portfolio. Under a reverse repurchase agreement, NMG LLC will effectively pledge its assets as collateral to secure a short-term loan. Generally, the other party to the

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agreement makes the loan in an amount equal to a percentage of the fair value of the pledged collateral. At the maturity of the reverse repurchase agreement, the payor will be required to repay the loan and correspondingly receive back its collateral. While used as collateral, the assets continue to pay principal and interest which are for the benefit of NMG LLC.

          NMG LLC's use of reverse repurchase agreements, if any, involves many of the same risks involved in its use of leverage, as the proceeds from reverse repurchase agreements generally will be invested in additional securities. There is a risk that the market value of the securities acquired with the proceeds of a reverse repurchase agreement may decline below the price of the securities that it has sold but remains obligated to repurchase under the reverse repurchase agreement. In addition, there is a risk that the market value of the securities effectively pledged by NMG LLC may decline. If a buyer of securities under a reverse repurchase agreement were to file for bankruptcy or experience insolvency, NMG LLC may be adversely affected. Also, in entering into reverse repurchase agreements, NMG LLC would bear the risk of loss to the extent that the proceeds of such agreements at settlement are more than the fair value of the underlying securities being pledged. In addition, due to the interest costs associated with reverse repurchase agreements transactions, NMG LLC's net asset value would decline, and, in some cases, we may be worse off than if such instruments had not been used.

If NMG LLC is unable to obtain additional debt financing, our business could be materially adversely affected.

          NMG LLC may want to obtain additional debt financing, or need to do so upon maturity of its credit facility, in order to obtain funds which may be made available for investments. The revolving period under the credit facility ends on October 21, 2012, and the credit facility matures on October 21, 2014. If NMG LLC is unable to increase, renew or replace any such facility and enter into a new debt financing facility on commercially reasonable terms, its liquidity may be reduced significantly. In addition, if NMG LLC is unable to repay amounts outstanding under any such facilities and is declared in default or is unable to renew or refinance these facilities, it may not be able to make new investments or operate our business in the normal course. These situations may arise due to circumstances that NMG LLC may be unable to control, such as lack of access to the credit markets, a severe decline in the value of the U.S. dollar, a further economic downturn or an operational problem that affects third parties or NMG LLC, and could materially damage NMG LLC's business operations and, consequently, New Mountain Guardian's business, results of operations and financial condition.

An extended continuation of the disruption in the capital markets and the credit markets could adversely affect our business.

          As business development companies, New Mountain Guardian and NMG LLC must maintain their ability to raise additional capital for investment purposes. If New Mountain Guardian or NMG LLC is unable to access the capital markets or credit markets, NMG LLC may be forced to curtail its business operations and may be unable to pursue new investment opportunities. The capital markets and the credit markets have experienced extreme volatility in recent periods, and, as a result, there has been and will likely continue to be uncertainty in the financial markets in general. In addition, a prolonged period of market illiquidity may cause NMG LLC to reduce the volume of loans it originates and/or funds and adversely affect the value of our portfolio investments. Ongoing disruptive conditions in the financial industry and the impact of new legislation in response to those conditions could restrict NMG LLC's business operations and, consequently, could adversely impact New Mountain Guardian's business, results of operations and financial condition.

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          If the fair value of NMG LLC's assets declines substantially, it may fail to maintain the asset coverage ratios imposed upon it by the 1940 Act. Any such failure would affect NMG LLC's ability to issue senior securities, including borrowings, and pay distributions, which could materially impair its business operations. NMG LLC's liquidity could be impaired further by New Mountain Guardian's or NMG LLC's inability to access the capital markets or NMG LLC's inability to draw on existing or future credit facilities. For example, we cannot be certain that NMG LLC will be able to renew its credit facilities as they mature or to consummate new borrowing facilities to provide capital for normal operations, including new originations. Reflecting concern about the stability of the financial markets, many lenders and institutional investors have reduced or ceased providing funding to borrowers. This market turmoil and tightening of credit have led to increased market volatility and widespread reduction of business activity generally. In addition, adverse economic conditions due to these disruptive conditions could materially impact NMG LLC's ability to comply with the financial and other covenants in any existing or future credit facilities. If NMG LLC is unable to comply with these covenants, its business could be materially adversely affected, which could, as a result, materially adversely affect New Mountain Guardian's business, results of operations and financial condition.

Because NMG LLC intends to make distributions to its members that will be sufficient to enable New Mountain Guardian to obtain and maintain its status as a RIC, and because New Mountain Guardian intends to distribute substantially all of its income to its stockholders to obtain and maintain its status as a RIC, New Mountain Guardian and NMG LLC will continue to need additional capital to finance our growth. If additional funds are unavailable or not available on favorable terms, our ability to grow will be impaired.

          In order for New Mountain Guardian to qualify for the tax benefits available to RICs and to avoid payment of excise taxes, NMG LLC intends to make distributions to its members that will be sufficient to enable New Mountain Guardian to obtain and maintain its status as a RIC, and New Mountain Guardian intends to distribute to its stockholders substantially all of its annual taxable income, except that it may retain certain net capital gains for reinvestment in common membership units of NMG LLC, and treat such amounts as deemed distributions to its stockholders. If New Mountain Guardian elects to treat any amounts as deemed distributions, New Mountain Guardian must pay income taxes at the corporate rate on such deemed distributions on behalf of its stockholders. As a result of these requirements, New Mountain Guardian and NMG LLC will likely need to raise capital from other sources to grow our business. As a business development company, NMG LLC generally will be required to meet a coverage ratio of total assets, less liabilities and indebtedness not represented by senior securities, to total senior securities, which includes all of NMG LLC's borrowings and any outstanding preferred membership units, of at least 200%. Because New Mountain Guardian will have no assets other than its ownership of common membership units of NMG LLC and will have no material long-term liabilities, New Mountain Guardian will look to NMG LLC's assets for purposes of satisfying this test. These requirements limit the amount that NMG LLC may borrow. Because NMG LLC will continue to need capital to grow our investment portfolio, these limitations may prevent NMG LLC from incurring debt and require NMG LLC or New Mountain Guardian to raise additional equity at a time when it may be disadvantageous to do so. While we expect NMG LLC will be able to borrow and to issue additional debt securities and expect that New Mountain Guardian will be able to issue additional equity securities, which would in turn increase the equity capital available to NMG LLC, we cannot assure you that debt and equity financing will be available to New Mountain Guardian or NMG LLC on favorable terms, or at all. In addition, as a business development company, New Mountain Guardian generally will not be permitted to issue equity securities priced below net asset value without stockholder approval. If additional funds are not available to New Mountain Guardian or NMG LLC,

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NMG LLC could be forced to curtail or cease new investment activities, and NMG LLC's net asset value and, consequently, New Mountain Guardian's net asset value, could decline.

Our ability to enter into transactions with our affiliates is restricted.

          As business development companies, New Mountain Guardian and NMG LLC will be prohibited under the 1940 Act from participating in certain transactions with their respective affiliates without the prior approval of their respective independent directors and, in some cases, the SEC. Any person that owns, directly or indirectly, 5% or more of New Mountain Guardian's outstanding voting securities will be New Mountain Guardian's and NMG LLC's affiliate for purposes of the 1940 Act. New Mountain Guardian and NMG LLC will generally be prohibited from buying or selling any securities (other than their respective securities) from or to an affiliate. The 1940 Act also prohibits certain "joint" transactions with an affiliate, which could include investments in the same portfolio company (whether at the same or different times), without prior approval of independent directors and, in some cases, the SEC. If a person acquires more than 25% of New Mountain Guardian's voting securities, New Mountain Guardian and NMG LLC are prohibited from buying or selling any security (other than their respective securities) from or to such person or certain of that person's affiliates, or entering into prohibited joint transactions with such persons, absent the prior approval of the SEC. Similar restrictions limit New Mountain Guardian's and NMG LLC's ability to transact business with their respective officers or directors or their affiliates. As a result of these restrictions, NMG LLC may be prohibited from buying or selling any security from or to any portfolio company of a private equity fund managed by any affiliate of the Investment Advisor without the prior approval of the SEC, which may limit the scope of investment opportunities that would otherwise be available to NMG LLC.

New Mountain Guardian and NMG LLC expect to file an application with the SEC requesting exemptive relief from certain provisions of the 1940 Act and the Securities Exchange Act of 1934.

          The 1940 Act prohibits certain transactions between New Mountain Guardian, NMG LLC and their respective affiliates without first obtaining an exemptive order from the SEC. New Mountain Guardian and NMG LLC expect to file an application with the SEC requesting an order exempting them from certain provisions of the 1940 Act and from certain reporting requirements mandated by the Securities Exchange Act of 1934, or the Exchange Act. If this relief is granted, NMG LLC would be exempt from the reporting obligations under the Exchange Act. However, New Mountain Guardian would continue to be required to file these reports with respect to its ownership in NMG LLC. There may be delays and costs involved in obtaining this relief, and there is no assurance that the application for exemptive relief will be granted by the SEC. New Mountain Guardian and NMG LLC also intend to seek exemptive relief to permit NMG LLC to pay the incentive fee payable to the Investment Advisor in common membership units of NMG LLC, which will be exchangeable into shares of New Mountain Guardian's common stock. See "— NMG LLC's ability to pay 100%, on an after tax basis, of the incentive fee to the Investment Advisor in common membership units of NMG LLC is contingent on receipt of exemptive relief from the SEC".

The Investment Advisor has significant potential conflicts of interest with New Mountain Guardian and NMG LLC and, consequently, your interests as stockholders which could adversely impact our investment returns.

          New Mountain Guardian's and NMG LLC's executive officers and directors, as well as the current or future investment professionals of the Investment Advisor, serve or may serve as officers, directors or principals of entities that operate in the same or a related line of business as we do or of investment funds managed by New Mountain Guardian's and NMG LLC's affiliates. Accordingly,

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they may have obligations to investors in those entities, the fulfillment of which might not be in your interests as stockholders. Although we are currently New Mountain's only vehicle focused primarily on investing in the Target Securities, in the future, the investment professionals of the Investment Advisor and/or New Mountain employees that provide services pursuant to the Investment Management Agreement may manage other funds which may from time to time have overlapping investment objectives with our own and, accordingly, may invest in, whether principally or secondarily, asset classes similar to those targeted by us. If this occurs, the Investment Advisor may face conflicts of interest in allocating investment opportunities to NMG LLC and such other funds. Although the investment professionals will endeavor to allocate investment opportunities in a fair and equitable manner, it is possible that NMG LLC may not be given the opportunity to participate in certain investments made by the Investment Advisor or persons affiliated with the Investment Advisor or that certain of these investment funds may be favored over NMG LLC. When these investment professionals identify an investment, they will be forced to choose which investment fund should make the investment.

          If the Investment Advisor forms other affiliates in the future, NMG LLC may co-invest on a concurrent basis with such other affiliate, subject to compliance with applicable regulations and regulatory guidance or an exemptive order from the SEC and NMG LLC's allocation procedures. In addition, NMG LLC pays management and incentive fees to the Investment Advisor and reimburses the Investment Advisor for certain expenses it incurs. As a result, investors in New Mountain Guardian's common stock will invest in New Mountain Guardian and indirectly in NMG LLC, on a "gross" basis and receive distributions on a "net" basis after New Mountain Guardian's pro rata share of NMG LLC's expenses, resulting in a lower rate of return than an investor might achieve through direct investments. Also, the incentive fee payable to the Investment Advisor may create an incentive for the Investment Advisor to pursue investments that are riskier or more speculative than would be the case in the absence of such compensation arrangements. Any potential conflict of interest arising as a result of the arrangements with the Investment Advisor could have a material adverse effect on our business, results of operations and financial condition.

The incentive fee NMG LLC pays to the Investment Advisor in respect of capital gains may be effectively greater than 20%.

          As a result of the operation of the cumulative method of calculating the capital gains portion of the incentive fee NMG LLC will pay to the Investment Advisor, the cumulative aggregate capital gains fee received by the Investment Advisor could be effectively greater than 20%, depending on the timing and extent of subsequent net realized capital losses or net unrealized depreciation. For additional information on this calculation, see the disclosure in footnote 2 to Example 2 under the caption "Investment Management Agreement — Overview of the Investment Advisor — Management Fee — Incentive Fee". We cannot predict whether, or to what extent, this payment calculation would affect your investment in New Mountain Guardian's common stock.

The Investment Advisor's investment committee, the Investment Advisor or its affiliates may, from time to time, possess material non-public information, limiting NMG LLC's investment discretion.

          The Investment Advisor's investment professionals, investment committee or their respective affiliates may serve as directors of, or in a similar capacity with, companies in which we invest through NMG LLC, the securities of which are purchased or sold on NMG LLC's behalf. In the event that material non-public information is obtained with respect to such companies, or we became subject to trading restrictions under the internal trading policies of those companies or as a result of applicable law or regulations, NMG LLC could be prohibited for a period of time from purchasing

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or selling the securities of such companies, and this prohibition may have an adverse effect on NMG LLC and, consequently, your interests as stockholders of New Mountain Guardian.

The valuation process for certain of our portfolio holdings creates a conflict of interest.

          Some of our portfolio investments are expected to be made in the form of securities that are not publicly traded. As a result, NMG LLC's board of directors will determine the fair value of these securities in good faith. In connection with this determination, investment professionals from New Mountain Guardian Advisors may provide NMG LLC's board of directors with portfolio company valuations based upon the most recent portfolio company financial statements available and projected financial results of each portfolio company. In addition, Steven Klinsky, a member of New Mountain Guardian's and NMG LLC's board of directors, has an indirect pecuniary interest in New Mountain Guardian Advisors. The participation of the Investment Advisor's investment professionals in our valuation process, and the indirect pecuniary interest in New Mountain Guardian Advisors by a member of New Mountain Guardian's and NMG LLC's board of directors, could result in a conflict of interest as New Mountain Guardian Advisors' management fee is based, in part, on NMG LLC's gross assets and incentive fees will be based, in part, on unrealized gains and losses.

Conflicts of interest may exist related to other arrangements with the Investment Advisor or its affiliates.

          New Mountain Guardian and NMG LLC have entered into a royalty-free license agreement with New Mountain under which New Mountain has agreed to grant New Mountain Guardian and NMG LLC a non-exclusive, royalty-free license to use the name "New Mountain". See "License Agreement". In addition, NMG LLC will reimburse New Mountain Guardian Administration for the allocable portion of overhead and other expenses incurred by New Mountain Guardian Administration in performing its obligations to New Mountain Guardian and NMG LLC under the Administration Agreement, such as rent and the allocable portion of the cost of New Mountain Guardian's and NMG LLC's chief financial officer and chief compliance officer and their respective staffs. This could create conflicts of interest that the board of directors for New Mountain Guardian and NMG LLC must monitor.

The Investment Management Agreement with New Mountain Guardian Advisors and the Administration Agreement with New Mountain Guardian Administration were not negotiated on an arm's length basis and may not be as favorable to NMG LLC and, consequently, New Mountain Guardian, than if they had been negotiated with an unaffiliated third party.

          The Investment Management Agreement and the Administration Agreement were negotiated between related parties. Consequently, their terms, including fees payable to New Mountain Guardian Advisors, may not be as favorable than if they had been negotiated with an unaffiliated third party. In addition, New Mountain Guardian and NMG LLC may choose not to enforce, or to enforce less vigorously, their respective rights and remedies under these agreements because of their desire to maintain their ongoing relationship with New Mountain Guardian Advisors, New Mountain Guardian Administration and their respective affiliates. Any such decision, however, could cause New Mountain Guardian to breach its fiduciary obligations to its stockholders.

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The Investment Advisor's liability will be limited under the Investment Management Agreement, and NMG LLC has agreed to indemnify the Investment Advisor against certain liabilities, which may lead the Investment Advisor to act in a riskier manner than it would when acting for its own account.

          Under the Investment Management Agreement, the Investment Advisor will not assume any responsibility other than to render the services called for under that agreement, and it will not be responsible for any action of NMG LLC's board of directors in following or declining to follow the Investment Advisor's advice or recommendations. The Investment Advisor maintains a contractual, as opposed to a fiduciary, relationship with NMG LLC. Under the terms of the Investment Management Agreement, the Investment Advisor, its officers, members, personnel, any person controlling or controlled by the Investment Advisor will not be liable to New Mountain Guardian, NMG LLC, any of their subsidiaries or any of their respective directors, members or stockholders or any subsidiary's stockholders or partners for acts or omissions performed in accordance with and pursuant to the Investment Management Agreement, except those resulting from acts constituting gross negligence, willful misconduct, bad faith or reckless disregard of the Investment Advisor's duties under the Investment Management Agreement. In addition, NMG LLC has agreed to indemnify the Investment Advisor and each of its officers, directors, members, managers and employees from and against any claims or liabilities, including reasonable legal fees and other expenses reasonably incurred, arising out of or in connection with our business and operations or any action taken or omitted pursuant to authority granted by the Investment Management Agreement, except where attributable to gross negligence, willful misconduct, bad faith or reckless disregard of such person's duties under the Investment Management Agreement. These protections may lead the Investment Advisor to act in a riskier manner than it would when acting for its own account.

The Investment Advisor can resign upon 60 days' notice, and a suitable replacement may not be found within that time, resulting in disruptions in NMG LLC's operations that could adversely affect our business, results of operations and financial condition.

          Under the Investment Management Agreement, the Investment Advisor has the right to resign at any time upon 60 days' written notice, whether a replacement has been found or not. If the Investment Advisor resigns, NMG LLC may not be able to find a new investment advisor or hire internal management with similar expertise and ability to provide the same or equivalent services on acceptable terms within 60 days, or at all. If a replacement is not able to be found on a timely basis, our business, results of operations and financial condition and NMG LLC's ability to pay distributions are likely to be adversely affected and the market price of New Mountain Guardian's common stock may decline. In addition, if NMG LLC is unable to identify and reach an agreement with a single institution or group of executives having the expertise possessed by the Investment Advisor and its affiliates, the coordination of its internal management and investment activities is likely to suffer. Even if NMG LLC is able to retain comparable management, whether internal or external, the integration of such management and their lack of familiarity with our investment objective may result in additional costs and time delays that may adversely affect our business, results of operations and financial condition.

The Administrator can resign from its role as Administrator under the Administration Agreement, and a suitable replacement may not be found, resulting in disruptions that could adversely affect our business, results of operations and financial condition.

          New Mountain Guardian Administration has the right to resign under the Administration Agreement, whether a replacement has been found or not. If New Mountain Guardian Administration resigns, it may be difficult to find a new administrator or hire internal management

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with similar expertise and ability to provide the same or equivalent services on acceptable terms, or at all. If a replacement is not found quickly, our business, results of operations and financial condition as well as NMG LLC's ability to pay distributions are likely to be adversely affected and the market price of New Mountain Guardian's common stock may decline. In addition, the coordination of New Mountain Guardian's and NMG LLC's internal management and administrative activities is likely to suffer if they are unable to identify and reach an agreement with a service provider or individuals with the expertise possessed by New Mountain Guardian Administration. Even if a comparable service provider or individuals to perform such services are retained, whether internal or external, their integration into our business and lack of familiarity with our investment objective may result in additional costs and time delays that may adversely affect our business, results of operations and financial condition.

If New Mountain Guardian and NMG LLC fail to maintain their status as business development companies, our business and operating flexibility could be significantly reduced.

          New Mountain Guardian and NMG LLC intend to qualify as business development companies under the 1940 Act immediately prior to the completion of this offering. The 1940 Act imposes numerous constraints on the operations of business development companies. For example, business development companies are required to invest at least 70% of their total assets in specified types of securities, primarily in private companies or thinly-traded U.S. public companies, cash, cash equivalents, U.S. government securities and other high quality debt investments that mature in one year or less. Failure to comply with the requirements imposed on business development companies by the 1940 Act could cause the SEC to bring an enforcement action against New Mountain Guardian or NMG LLC and/or expose New Mountain Guardian or NMG LLC to claims of private litigants. In addition, upon approval of a majority of New Mountain Guardian's stockholders, or, in NMG LLC's case, a majority of its members voting on a pass through basis, New Mountain Guardian or NMG LLC may elect to withdraw their respective election as a business development company. If New Mountain Guardian or NMG LLC decide to withdraw their election, or if New Mountain Guardian or NMG LLC otherwise fail to qualify, or maintain their qualification, as a business development company, New Mountain Guardian or NMG LLC may be subject to the substantially greater regulation under the 1940 Act as a closed-end investment company. Compliance with these regulations would significantly decrease our operating flexibility and could significantly increase our cost of doing business. For additional information on the qualification requirements of a business development company, see the disclosure under the caption "Regulation".

If NMG LLC does not invest a sufficient portion of its assets in qualifying assets, it could be precluded from investing in certain assets or could be required to dispose of certain assets, which could have a material adverse effect on our business, financial condition and results of operations.

          As a business development company, NMG LLC will be prohibited from acquiring any assets other than "qualifying assets" unless, at the time of and after giving effect to such acquisition, at least 70% of our total assets are qualifying assets. As of                    , 2010, approximately $              million, or approximately         %, of NMG LLC's total assets were not "qualifying assets". We expect that substantially all of NMG LLC's assets that it may acquire in the future will be "qualifying assets", although it may decide to make other investments that are not "qualifying assets" to the extent permitted by the 1940 Act. If NMG LLC does not invest a sufficient portion of its assets in qualifying assets, it would be prohibited from investing in additional assets, which could have a material adverse effect on our business, financial condition and results of operations. Similarly, these rules could prevent NMG LLC from making follow-on investments in existing portfolio companies (which could result in the dilution of its position) or could require NMG LLC to

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dispose of investments at inopportune times in order to come into compliance with the 1940 Act. If NMG LLC needs to dispose of these investments quickly, it may be difficult to dispose of such investments on favorable terms. For example, NMG LLC may have difficulty in finding a buyer and, even if a buyer is found, it may have to sell the investments at a substantial loss.

NMG LLC's ability to invest in public companies may be limited in certain circumstances.

          To maintain NMG LLC's status, and consequently, New Mountain Guardian's status as business development companies, NMG LLC is not permitted to acquire any assets other than "qualifying assets" specified in the 1940 Act unless, at the time the acquisition is made, at least 70% of its total assets are qualifying assets (with certain limited exceptions). Subject to certain exceptions for follow-on investments and distressed companies, an investment in an issuer that has outstanding securities listed on a national securities exchange may be treated as qualifying assets only if such issuer has a common equity market capitalization that is less than $250 million at the time of such investment.

Regulations governing the operations of business development companies will affect New Mountain Guardian's ability to raise additional equity capital as well as NMG LLC's ability to issue senior securities or borrow for investment purposes, any or all of which could have a negative effect on our investment objectives and strategies.

          Our business will require a substantial amount of capital in addition to the proceeds of this offering and the concurrent private placement. NMG LLC may acquire additional capital from the issuance of senior securities, including borrowing or other indebtedness. In addition, New Mountain Guardian may also issue additional equity capital, which would in turn increase the equity capital available to NMG LLC. Under the 1940 Act, New Mountain Guardian is not permitted to own any other securities other than common membership units of NMG LLC. As a result, any proceeds from offerings of New Mountain Guardian's equity securities would be contributed to NMG LLC and subsequently used by NMG LLC for investment purposes. However, New Mountain Guardian and NMG LLC may not be able to raise additional capital in the future on favorable terms or at all.

          NMG LLC may issue debt securities, other evidences of indebtedness or preferred membership units, and it may borrow money from banks or other financial institutions, which we refer to collectively as "senior securities", up to the maximum amount permitted by the 1940 Act. The 1940 Act permits NMG LLC to issue senior securities in amounts such that its asset coverage, as defined in the 1940 Act, equals at least 200% after each issuance of senior securities. NMG LLC would be unable to pay dividends or issue additional senior securities, and, consequently, New Mountain Guardian would be unable to pay dividends, if NMG LLC's asset coverage ratio were not at least 200%. If the value of NMG LLC's assets declines, it may be unable to satisfy this test. If that happens, NMG LLC may be required to liquidate a portion of our investments and repay a portion of its indebtedness at a time when such sales may be disadvantageous.

          In addition, NMG LLC may in the future seek to securitize our portfolio securities to generate cash for funding new investments. To securitize loans, NMG LLC would likely create a wholly-owned subsidiary and contribute a pool of loans to the subsidiary. NMG LLC would then sell interests in the subsidiary on a non-recourse basis to purchasers and it would retain all or a portion of the equity in the subsidiary. If NMG LLC is unable to successfully securitize our loan portfolio, its ability to grow our business or fully execute our business strategy could be impaired and our earnings, if any, could decrease. The securitization market is subject to changing market conditions and NMG LLC may not be able to access this market when it would otherwise deem appropriate. Moreover, the successful securitization of our portfolio might expose NMG LLC to losses as the residual investments in which it does not sell interests will tend to be those that are riskier and

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more apt to generate losses. The 1940 Act also may impose restrictions on the structure of any securitization.

          New Mountain Guardian may also obtain capital for use by NMG LLC through the issuance of additional equity capital, which would in turn increase the equity capital available to NMG LLC. As a business development company, New Mountain Guardian generally is not able to issue or sell its common stock at a price below net asset value per share. If New Mountain Guardian's common stock trades at a discount to its net asset value per share, this restriction could adversely affect its ability to raise equity capital. New Mountain Guardian may, however, sell its common stock, or warrants, options or rights to acquire its common stock, at a price below its current net asset value per share of the common stock if its board of directors and independent directors determine that such sale is in its best interests and the best interests of its stockholders, and its stockholders approve such sale. In any such case, the price at which New Mountain Guardian's securities are to be issued and sold may not be less than a price that, in the determination of New Mountain Guardian's board of directors, closely approximates the market value of such securities (less any underwriting commission or discount). If New Mountain Guardian raises additional funds by issuing more shares of its common stock or if NMG LLC issues senior securities convertible into, or exchangeable for, New Mountain Guardian's common stock, the percentage ownership of New Mountain Guardian's stockholders may decline and you may experience dilution. Any proceeds from the issuance of additional shares of New Mountain Guardian's common stock would be contributed to NMG LLC and used to purchase, on a one-for-one basis, additional common membership units of NMG LLC.

NMG LLC's ability to pay 100%, on an after tax basis, of the incentive fee to the Investment Advisor in common membership units of NMG LLC is contingent on receipt of exemptive relief from the SEC.

          Pursuant to the Investment Management Agreement with the Investment Advisor, NMG LLC has agreed, to the extent permissible, to pay 100%, on an after tax basis, of the incentive fee in common membership units of NMG LLC having a total net asset value equal to the amount of the incentive fee, which common memberships units will be exchangeable into shares of New Mountain Guardian's common stock on a one-for-one basis. Under the 1940 Act, NMG LLC is prohibited from issuing common membership units for services unless and until it obtains from the SEC an exemptive order permitting such practice. New Mountain Guardian and NMG LLC will apply for an exemptive order from the SEC to permit NMG LLC to pay 100%, on an after tax basis, of the incentive fee to the Investment Advisor by issuing common membership units to the Investment Advisor. The SEC is not obligated to grant an exemptive order to allow this practice and will do so only if it determines that such practice is consistent with stockholder and member interests and does not involve overreaching by NMG LLC's management or board of directors. In addition, Section 16 of the Exchange Act imposes short swing profit liability on directors, officers and 10 percent owners of securities who purchase and sell those securities within a six-month period. In order to avoid potential short-swing profit liability as a result of receiving its incentive fee in common membership units, New Mountain Guardian and NMG LLC will also apply for an exemptive order to treat the receipt of such common membership units and any common stock received upon exchange of such common membership units as an exempt purchase under Section 16 of the Exchange Act. The SEC is not obligated to grant such an order and there can be no assurance they will do so. If both forms of exemptive relief are not granted, NMG LLC will pay the entire incentive fee in cash, which would reduce the amount of cash available for NMG LLC to use for additional investments. This could, in turn, require NMG LLC to forego otherwise attractive investment opportunities.

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Our business model in the future may depend to an extent upon our referral relationships with private equity sponsors, and the inability of the investment professionals of the Investment Advisor to maintain or develop these relationships, or the failure of these relationships to generate investment opportunities, could adversely affect our business strategy.

          Although all of our existing investments were made in open-market secondary purchases, future investments could be made through primary originations. If this occurs, we may need to depend to an extent upon the relationships the investment professionals of the Investment Advisor have with private equity sponsors to provide us with potential investment opportunities. If the investment professionals of the Investment Advisor fail to maintain existing relationships or develop new relationships with other sponsors or sources of investment opportunities, NMG LLC will not be able to grow our investment portfolio. In addition, individuals with whom the investment professionals of the Investment Advisor have relationships are not obligated to provide us with investment opportunities, and, therefore, there is no assurance that any relationships they currently or may in the future have will generate investment opportunities for us.

We may experience fluctuations in our annual and quarterly results due to the nature of our business.

          We could experience fluctuations in our annual and quarterly operating results due to a number of factors, some of which are beyond our control, including the ability or inability to make investments in companies that meet our investment criteria, the interest rate payable on the debt securities acquired and the default rate on such securities, the level of our expenses, variations in and the timing of the recognition of realized and unrealized gains or losses, the degree to which we encounter competition in the markets in which we operate and general economic conditions. As a result of these factors, results for any period should not be relied upon as being indicative of performance in future periods.

NMG LLC's board of directors may change our investment objective, operating policies and strategies without prior notice or member approval, the effects of which may be adverse to your interest as a stockholder.

          NMG LLC's board of directors has the authority, except as otherwise provided in the 1940 Act, to modify or waive certain of our operating policies and strategies without prior notice and without member approval. As a result, NMG LLC's board of directors will be able to change our investment policies and objectives without any input from New Mountain Guardian and its stockholders. However, absent member approval, voting on a pass through basis, NMG LLC may not change the nature of its business so as to cease to be, or withdraw its election as, a business development company. Under Delaware law and the LLC Agreement, NMG LLC also cannot be dissolved without prior member approval, voting on a pass through basis. Following the completion of this offering, the stockholders of New Mountain Guardian will collectively own through their investment in New Mountain Guardian approximately          % of the common membership units of NMG LLC. As a result, the stockholders of New Mountain Guardian, collectively, may not be able to influence the outcome of matters requiring a vote, on a pass through basis, of the members of NMG LLC, and your ability to terminate the Investment Management Agreement may be limited. We cannot predict the effect any changes to our current operating policies and strategies would have on our business, operating results and the market price of New Mountain Guardian's common stock. Nevertheless, any such changes could adversely affect our business and impair NMG LLC's ability to make distributions to its members, and, consequently, New Mountain Guardian's ability to make distributions to its stockholders.

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New Mountain Guardian will be subject to corporate-level federal income tax on all of its income if it is unable to qualify as a RIC under Subchapter M of the Code, which would have a material adverse effect on its financial performance.

          Although New Mountain Guardian intends to elect to be treated, and intends to qualify annually, as a RIC under Subchapter M of the Code, commencing with its taxable year ending December 31, 2010, no assurance can be given that New Mountain Guardian will be able to qualify for and maintain RIC status. To obtain and maintain RIC status and be relieved of federal income taxes on income and gains distributed to its stockholders, New Mountain Guardian must meet the annual distribution, source-of-income and asset diversification requirements described below. However, New Mountain Guardian will have no assets, other than its direct ownership of common membership units of NMG LLC, and no source of cash flow, other than distributions from NMG LLC, and New Mountain Guardian will not be permitted to conduct any business or ventures, other than in connection with the acquisition, ownership or disposition of common membership units of NMG LLC and its operation as a public reporting company. Accordingly, New Mountain Guardian will look to NMG LLC's assets and income, and will rely on the distributions made by NMG LLC to its members, for purposes of satisfying these requirements.

•

The annual distribution requirement for a RIC will be satisfied if New Mountain Guardian distributes to its stockholders on an annual basis at least 90% of its net ordinary income and realized net short-term capital gains in excess of realized net long-term capital losses, if any. Because NMG LLC may use debt financing, it is subject to an asset coverage ratio requirement under the 1940 Act and may be subject to certain financial covenants under its debt financing agreements that could, under certain circumstances, restrict it from making distributions to its members necessary for New Mountain Guardian to satisfy the distribution requirement. If NMG LLC is unable to obtain cash from other sources, and thus is unable to make sufficient distributions to its members, New Mountain Guardian could fail to qualify for RIC tax treatment and thus become subject to corporate-level federal income tax (and any applicable state and local taxes).



•

The source-of-income requirement will be satisfied if at least 90% of New Mountain Guardian's allocable share of NMG LLC's gross income for each year is derived from dividends, interest, gains from the sale of stock or securities or similar sources.



•

The asset diversification requirement will be satisfied if New Mountain Guardian meets certain asset diversification requirements at the end of each quarter of its taxable year. To satisfy this requirement, at least 50% of the value of New Mountain Guardian's assets must consist of cash, cash equivalents, U.S. government securities, securities of other RICs, and other acceptable securities; and no more than 25% of the value of New Mountain Guardian's assets can be invested in the securities, other than U.S. government securities or securities of other RICs, of one issuer, of two or more issuers that are controlled, as determined under applicable Code rules, by it and that are engaged in the same or similar or related trades or businesses or of certain "qualified publicly traded partnerships". Failure to meet these requirements may result in NMG LLC having to dispose of certain investments quickly in order to prevent the loss of New Mountain Guardian's RIC status. Because most of our investments will be in private companies, and therefore will be relatively illiquid, any such dispositions could be made at disadvantageous prices and could result in substantial losses. For purposes of applying the asset diversification requirement, although there is no authority directly applicable to New Mountain Guardian and thus the matter is not free from doubt, it is expected that New Mountain Guardian will be treated as if it directly invested in its pro rata share of NMG LLC's assets for purposes of satisfying the asset diversification requirement. However, there can be no assurance that the IRS will not successfully assert that New Mountain Guardian does not meet the asset diversification requirement because it is unable to look to NMG LLC's assets for purpose of that requirement. In that case, New

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Mountain Guardian would fail to qualify as a RIC and thus become subject to corporate-level federal income tax (and any applicable state and local taxes).

          If New Mountain Guardian fails to qualify for or maintain its RIC status for any reason and is subject to corporate-level federal income tax (and any applicable state and local taxes), the resulting taxes could substantially reduce its net assets, the amount of income available for distribution and the amount of its distributions, which would have a material adverse effect on its financial performance. For additional discussion regarding the tax implications of a RIC, see "Material Federal Income Tax Considerations — Taxation of New Mountain Guardian as a RIC" and "Material Federal Income Tax Considerations — Failure of New Mountain Guardian to Qualify as a RIC".

You may have current tax liabilities on distributions you reinvest in common stock of New Mountain Guardian.

          Under the dividend reinvestment plan, if you own shares of common stock of New Mountain Guardian registered in your own name, you will have all cash distributions automatically reinvested in additional shares of common stock of New Mountain Guardian unless you opt out of the dividend reinvestment plan by delivering a written notice to the plan administrator prior to the record date of the next dividend or distribution. If you have not "opted out" of the dividend reinvestment plan, you will be deemed to have received, and for federal income tax purposes will be taxed on, the amount reinvested in common stock of New Mountain Guardian to the extent the amount reinvested was not a tax-free return of capital. As a result, you may have to use funds from other sources to pay your federal income tax liability on the value of the common stock received. See "Dividend Reinvestment Plan".

New Mountain Guardian may not be able to pay you distributions on its common stock, its distributions to you may not grow over time and a portion of its distributions to you may be a return of capital for federal income tax purposes.

          New Mountain Guardian intends to pay quarterly distributions to its stockholders out of assets legally available for distribution. We cannot assure you that we will achieve investment results that will allow New Mountain Guardian to make a specified level of cash distributions or year-to-year increases in cash distributions. If NMG LLC is are unable to satisfy the asset coverage test applicable to it as a business development company, NMG LLC's ability to pay distributions to its members could be limited, thereby limiting New Mountain Guardian Corporation's ability to pay distributions to its stockholders. All distributions will be paid at the discretion of NMG LLC's board of directors and will depend on its earnings, financial condition, maintenance of New Mountain Guardian's RIC status, compliance with applicable business development company regulations and such other factors as NMG LLC's board of directors may deem relevant from time to time. The distributions New Mountain Guardian pays to its stockholders in a year may exceed its taxable income for that year and, accordingly, a portion of such distributions may constitute a return of capital for federal income tax purposes.

          In addition, because New Mountain Guardian will be a holding company, New Mountain Guardian will only be able to pay distributions on its common stock from distributions received from NMG LLC. NMG LLC intends to make distributions to its members that will be sufficient to enable New Mountain Guardian to pay quarterly distributions to its stockholders and to obtain and maintain its status as a RIC. However, there can be no assurances that NMG LLC will make distributions to its members in the future. Accordingly, New Mountain Guardian cannot assure you that it will pay distributions to you in the future.

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New Mountain Guardian may have difficulty paying its required distributions if NMG LLC recognizes taxable income before or without receiving cash representing such income.

          For federal income tax purposes, New Mountain Guardian will include in its taxable income its allocable share of certain amounts that NMG LLC has not yet received in cash, such as original issue discount or accruals on a contingent payment debt instrument, which may occur if NMG LLC receives warrants in connection with the origination of a loan or possibly in other circumstances or contracted payment-in-kind, or PIK, interest, which generally represents contractual interest added to the loan balance and due at the end of the loan term. New Mountain Guardian's allocable share of such original issue discount and PIK interest will be included in New Mountain Guardian's taxable income before NMG LLC receives any corresponding cash payments. New Mountain Guardian also may be required to include in its taxable income its allocable share of certain other amounts that NMG LLC will not receive in cash.

          Because in certain cases NMG LLC may recognize taxable income before or without receiving cash representing such income, NMG LLC may have difficulty making distributions to NMG LLC's members that will be sufficient to enable New Mountain Guardian to meet the annual distribution requirement necessary for New Mountain Guardian to qualify as a RIC. Accordingly, NMG LLC may need to sell some of NMG LLC's assets at times and/or at prices that NMG LLC would not consider advantageous, New Mountain Guardian or NMG LLC may need to raise additional equity or debt capital or NMG LLC may need to forego new investment opportunities or otherwise take actions that are disadvantageous to NMG LLC's business (or be unable to take actions that are advantageous to NMG LLC's business) to enable NMG LLC to make distributions to its members that will be sufficient to enable New Mountain Guardian to meet the annual distribution requirement. If New Mountain Guardian or NMG LLC is unable to obtain cash from other sources to enable New Mountain Guardian to meet the annual distribution requirement, New Mountain Guardian may fail to qualify for the federal income tax benefits allowable to RICs and, thus, become subject to a corporate-level federal income tax (and any applicable state and local taxes). For additional discussion regarding the tax implications of a RIC, see "Material Federal Income Tax Considerations — Taxation of New Mountain Guardian as a RIC" and "Material Federal Income Tax Considerations — Failure of New Mountain Guardian to Qualify as a RIC".

Changes in laws or regulations governing our operations may adversely affect our business or cause us to alter our business strategy.

          Changes in the laws or regulations or the interpretations of the laws and regulations that govern business development companies, RICs or non-depository commercial lenders could significantly affect our operations and our cost of doing business. New Mountain Guardian, NMG LLC and our portfolio companies are subject to federal, state and local laws and regulations. New legislation may be enacted or new interpretations, rulings or regulations could be adopted, any of which could adversely affect our business, including with respect to the types of investments we are permitted to make, and your interest as a stockholder potentially with retroactive effect. In addition, any changes to the laws and regulations governing our operations relating to permitted investments may cause us to alter our investment strategy in order to avail ourselves of new or different opportunities. These changes could result in material changes to the strategies and plans set forth in this prospectus and may result in our investment focus shifting from the areas of expertise of the Investment Advisor to other types of investments in which the Investment Advisor may have less expertise or little or no experience. Any such changes, if they occur, could have a material adverse effect on our business, results of operations and financial condition and, consequently, the value of your investment in us.

New Mountain Guardian will incur significant costs as a result of being a publicly traded company.

          As a publicly traded company, New Mountain Guardian will incur legal, accounting and other expenses, which will be paid by NMG LLC, including costs associated with the periodic reporting

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requirements applicable to a company whose securities are registered under the Exchange Act, as well as additional corporate governance requirements, including requirements under the Sarbanes-Oxley Act of 2002, or the "Sarbanes-Oxley Act", and other rules implemented by the SEC. In addition, until exemptive relief is obtained, NMG LLC will also incur costs associated with its separate periodic reporting requirements under the Exchange Act. You will bear NMG LLC's expenses, as well as New Mountain Guardian's expenses, indirectly through New Mountain Guardian's investment in NMG LLC.

Efforts to comply with Section 404 of the Sarbanes-Oxley Act will involve significant expenditures, and non-compliance with Section 404 of the Sarbanes-Oxley Act may adversely affect New Mountain Guardian and the market price of New Mountain Guardian's common stock.

          Upon completion of this offering, New Mountain Guardian and NMG LLC will be subject to the Sarbanes-Oxley Act, and the related rules and regulations promulgated by the SEC. Under current SEC rules, beginning with New Mountain Guardian's fiscal year ending December 31, 2011, New Mountain Guardian's and NMG LLC's management will be required to report on their internal control over financial reporting pursuant to Section 404 of the Sarbanes-Oxley Act, and rules and regulations of the SEC thereunder. New Mountain Guardian and NMG LLC will be required to review on an annual basis their respective internal control over financial reporting, and on a quarterly and annual basis to evaluate and disclose changes in our respective internal control over financial reporting. As a result, New Mountain Guardian and NMG LLC expect to incur significant additional expenses in the near term, which may negatively impact NMG LLC's financial performance and NMG LLC's ability to make distributions to its members and, consequently, New Mountain Guardian's ability to make distributions to its stockholders. This process also will result in a diversion of management's time and attention. We cannot be certain as to the timing of completion of any evaluation, testing and remediation actions or the impact of the same on our operations and neither New Mountain Guardian nor NMG LLC may be able to ensure that the process is effective or that New Mountain Guardian's or NMG LLC's internal control over financial reporting is or will be effective in a timely manner. In the event that New Mountain Guardian and NMG LLC are unable to maintain or achieve compliance with Section 404 of the Sarbanes-Oxley Act and related rules, NMG LLC and, consequently, the market price of New Mountain Guardian's common stock may be adversely affected.

Our business is highly dependent on information systems and systems failures could significantly disrupt our business, which may, in turn, negatively affect the market price of New Mountain Guardian's common stock and its ability to pay dividends.

          Our business is highly dependent on the communications and information systems of the Investment Advisor and its affiliates. Any failure or interruption of such systems could cause delays or other problems in our activities. This, in turn, could have a material adverse effect on our operating results and, consequently, negatively affect the market price of New Mountain Guardian's common stock and its ability to pay dividends to its stockholders. In addition, because many of our portfolio companies operate and rely on network infrastructure and enterprise applications and internal technology systems for development, marketing, operational, support and other business activities, a disruption or failure of any or all of these systems in the event of a major telecommunications failure, cyber-attack, fire, earthquake, severe weather conditions or other catastrophic event could cause system interruptions, delays in product development and loss of critical data and could otherwise disrupt their business operations.

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Risks Relating to Our Investments

Our investments in portfolio companies may be risky, and we could lose all or part of our investment.

          Investing in middle-market businesses involves a number of significant risks. Among other things, these companies:

•

may have limited financial resources and may be unable to meet their obligations under their debt instruments that we hold, which may be accompanied by a deterioration in the value of any collateral and a reduction in the likelihood of us realizing any guarantees from subsidiaries or affiliates of our portfolio companies that we may have obtained in connection with our investment, as well as a corresponding decrease in the value of any equity components of our investments;



•

may have shorter operating histories, narrower product lines, smaller market shares and/or more significant customer concentrations than larger businesses, which tend to render them more vulnerable to competitors' actions and market conditions, as well as general economic downturns;



•

are more likely to depend on the management talents and efforts of a small group of persons; therefore, the death, disability, resignation or termination of one or more of these persons could have a material adverse impact on our portfolio company and, in turn, on us;



•

generally have less predictable operating results, may from time to time be parties to litigation, may be engaged in rapidly changing businesses with products subject to a substantial risk of obsolescence;



•

may require substantial additional capital to support their operations, finance expansion or maintain their competitive position; and



•

generally have less publicly available information about their businesses, operations and financial condition.

          In addition, in the course of providing significant managerial assistance to certain of our portfolio companies, certain of NMG LLC's officers and directors may serve as directors on the boards of such companies. To the extent that litigation arises out of our investments in these companies, NMG LLC's officers and directors may be named as defendants in such litigation, which could result in an expenditure of funds (through NMG LLC's indemnification of such officers and directors) and the diversion of management time and resources.

Our investment strategy, which is focused primarily on privately held companies, presents certain challenges, including the lack of available information about these companies.

          NMG LLC invests primarily in privately held companies. There is generally little public information about these companies, and, as a result, NMG LLC must rely on the ability of the Investment Advisor to obtain adequate information to evaluate the potential returns from, and risks related to, investing in these companies. If NMG LLC is unable to uncover all material information about these companies, it may not make a fully informed investment decision, and it may lose money on our investments. Also, privately held companies frequently have less diverse product lines and smaller market presence than larger competitors. They are, thus, generally more vulnerable to economic downturns and may experience substantial variations in operating results. These factors could adversely affect our investment returns.

If NMG LLC makes unsecured investments, those investments might not generate sufficient cash flow to service their debt obligations to NMG LLC.

          NMG LLC may make unsecured investments. Unsecured investments may be subordinated to other obligations of the obligor. Unsecured investments often reflect a greater possibility that adverse changes in the financial condition of the obligor or general economic conditions (including,

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for example, a substantial period of rising interest rates or declining earnings) or both may impair the ability of the obligor to make payment of principal and interest. If NMG LLC makes an unsecured investment in a portfolio company, that portfolio company may be highly leveraged, and its relatively high debt-to-equity ratio may increase the risk that its operations might not generate sufficient cash to service its debt obligations.

If NMG LLC invests in the securities and obligations of distressed and bankrupt issuers, it might not receive interest or other payments.

          From time to time, NMG LLC may invest in other types of investments which are not our primary focus, including investments in the securities and obligations of distressed and bankrupt issuers, including debt obligations that are in covenant or payment default. Such investments generally are considered speculative. The repayment of defaulted obligations is subject to significant uncertainties. Defaulted obligations might be repaid only after lengthy workout or bankruptcy proceedings, during which the issuer of those obligations might not make any interest or other payments.

The lack of liquidity in our investments may adversely affect our business.

          NMG LLC invests, and will continue to invest, in companies whose securities are not publicly traded and whose securities will be subject to legal and other restrictions on resale or will otherwise be less liquid than publicly traded securities. The illiquidity of these investments may make it difficult for NMG LLC to sell these investments when desired. In addition, if NMG LLC is required or otherwise chooses to liquidate all or a portion of our portfolio quickly, it may realize significantly less than the value at which it had previously recorded these investments. Our investments are usually subject to contractual or legal restrictions on resale or are otherwise illiquid because there is usually no established trading market for such investments. Because most of our investments are illiquid, NMG LLC may be unable to dispose of them in which case New Mountain Guardian could fail to qualify as a RIC and/or business development company, or NMG LLC may be unable to do so at a favorable price, and, as a result, NMG LLC and New Mountain Guardian may suffer losses.

Price declines and illiquidity in the corporate debt markets may adversely affect the fair value of our portfolio investments, reducing NMG LLC's net asset value through increased net unrealized depreciation.

          As a business development company, NMG LLC is required to carry our investments at market value or, if no market value is ascertainable, at fair value as determined in good faith by its board of directors. Because New Mountain Guardian will be a holding company with no direct operations of its own, and its only business and sole asset will be its ownership of common membership units of NMG LLC, New Mountain Guardian's net asset value will be based on NMG LLC's valuation of our investments and its percentage interest in NMG LLC. As part of the valuation process, NMG LLC may take into account the following types of factors, if relevant, in determining the fair value of our investments:

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a comparison of the portfolio company's securities to publicly traded securities;



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the enterprise value of a portfolio company;



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the nature and realizable value of any collateral;



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the portfolio company's ability to make payments and its earnings and discounted cash flow;



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the markets in which the portfolio company does business; and



•

changes in the interest rate environment and the credit markets generally that may affect the price at which similar investments may be made in the future and other relevant factors.

          When an external event such as a purchase transaction, public offering or subsequent sale occurs, NMG LLC will use the pricing indicated by the external event to corroborate its valuation.

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NMG LLC will record decreases in the market values or fair values of our investments as unrealized depreciation. Declines in prices and liquidity in the corporate debt markets may result in significant net unrealized depreciation in our portfolio. The effect of all of these factors on our portfolio may reduce NMG LLC's net asset value, and, indirectly, New Mountain Guardian's net asset value based on its percentage interest in NMG LLC, by increasing net unrealized depreciation in our portfolio. Depending on market conditions, NMG LLC could incur substantial realized losses and may suffer additional unrealized losses in future periods, which could have a material adverse effect on its business, financial condition, results of operations and cash flows.

If NMG LLC is unable to make follow-on investments in our portfolio companies, the value of our investment portfolio could be adversely affected.

          Following an initial investment in a portfolio company, NMG LLC may make additional investments in that portfolio company as "follow-on" investments, in order to (i) increase or maintain in whole or in part its equity ownership percentage, (ii) exercise warrants, options or convertible securities that were acquired in the original or subsequent financing or (iii) attempt to preserve or enhance the value of our investment. NMG LLC may elect not to make follow-on investments or may otherwise lack sufficient funds to make these investments. NMG LLC will have the discretion to make follow-on investments, subject to the availability of capital resources. If NMG LLC fails to make follow-on investments, the continued viability of a portfolio company and our investment may, in some circumstances, be jeopardized and we could miss an opportunity for NMG LLC to increase its participation in a successful operation. Even if NMG LLC has sufficient capital to make a desired follow-on investment, it may elect not to make a follow-on investment because it may not want to increase its concentration of risk, either because it prefers other opportunities or because it is subject to business development company requirements that would prevent such follow-on investments or such follow-on investments would adversely impact New Mountain Guardian's ability to maintain its RIC status.

Our portfolio companies may incur debt that ranks equally with, or senior to, our investments in such companies.

          NMG LLC invests in Target Securities at all levels of the capital structure. Our portfolio companies may have, or may be permitted to incur, other debt that ranks equally with, or senior to, the debt in which NMG LLC invests. By their terms, these debt instruments may entitle the holders to receive payment of interest or principal on or before the dates on which NMG LLC is entitled to receive payments with respect to the debt instruments in which it invests. In addition, in the event of insolvency, liquidation, dissolution, reorganization or bankruptcy of a portfolio company, holders of debt instruments ranking senior to NMG LLC's investment in that portfolio company would typically be entitled to receive payment in full before it receives any distribution. After repaying the senior creditors, the portfolio company may not have any remaining assets to use for repaying its obligation to NMG LLC. In the case of debt ranking equally with debt instruments in which NMG LLC invests, it would have to share on an equal basis any distributions with other creditors holding such debt in the event of an insolvency, liquidation, dissolution, reorganization or bankruptcy of the relevant portfolio company.

The disposition of our investments may result in contingent liabilities.

          Most of our investments will involve private securities. In connection with the disposition of an investment in private securities, NMG LLC may be required to make representations about the business and financial affairs of the portfolio company typical of those made in connection with the sale of a business. NMG LLC may also be required to indemnify the purchasers of such investment to the extent that any such representations turn out to be inaccurate or with respect to certain potential liabilities. These arrangements may result in contingent liabilities that ultimately yield funding obligations that must be satisfied through NMG LLC's return of certain distributions previously made to it.

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There may be circumstances where our debt investments could be subordinated to claims of other creditors or NMG LLC could be subject to lender liability claims.

          Even though NMG LLC may have structured certain of our investments as senior loans, if one of our portfolio companies were to go bankrupt, depending on the facts and circumstances, including the extent to which NMG LLC actually provided managerial assistance to that portfolio company, a bankruptcy court might recharacterize our debt investment and subordinate all or a portion of NMG LLC's claim to that of other creditors. NMG LLC may also be subject to lender liability claims for actions taken by it with respect to a borrower's business or instances where it exercises control over the borrower. It is possible that NMG LLC could become subject to a lender's liability claim, including as a result of actions taken in rendering significant managerial assistance.

Second priority liens on collateral securing loans that NMG LLC makes to our portfolio companies may be subject to control by senior creditors with first priority liens. If there is a default, the value of the collateral may not be sufficient to repay in full both the first priority creditors and NMG LLC.

          Certain loans to portfolio companies will be secured on a second priority basis by the same collateral securing senior secured debt of such companies. The first priority liens on the collateral will secure the portfolio company's obligations under any outstanding senior debt and may secure certain other future debt that may be permitted to be incurred by the company under the agreements governing the loans. The holders of obligations secured by the first priority liens on the collateral will generally control the liquidation of and be entitled to receive proceeds from any realization of the collateral to repay their obligations in full before NMG LLC. In addition, the value of the collateral in the event of liquidation will depend on market and economic conditions, the availability of buyers and other factors. There can be no assurance that the proceeds, if any, from the sale or sales of all of the collateral would be sufficient to satisfy the loan obligations secured by the second priority liens after payment in full of all obligations secured by the first priority liens on the collateral. If such proceeds are not sufficient to repay amounts outstanding under the loan obligations secured by the second priority liens, then NMG LLC, to the extent not repaid from the proceeds of the sale of the collateral, will only have an unsecured claim against the company's remaining assets, if any.

          The rights NMG LLC may have with respect to the collateral securing the loans it makes to our portfolio companies with senior debt outstanding may also be limited pursuant to the terms of one or more intercreditor agreements entered into with the holders of senior debt. Under an intercreditor agreement, at any time that obligations that have the benefit of the first priority liens are outstanding, any of the following actions that may be taken in respect of the collateral will be at the direction of the holders of the obligations secured by the first priority liens: the ability to cause the commencement of enforcement proceedings against the collateral, the ability to control the conduct of such proceedings, the approval of amendments to collateral documents; releases of liens on the collateral and waivers of past defaults under collateral documents. NMG LLC may not have the ability to control or direct these actions, even if its rights are adversely affected.

We generally will not control our portfolio companies.

          We do not, and do not expect to, control most of our portfolio companies, even though NMG LLC may have board representation or board observation rights, and our debt agreements may contain certain restrictive covenants that limit the business and operations of our portfolio companies. As a result, we are subject to the risk that a portfolio company may make business decisions with which we disagree and the management of such company, in which NMG LLC invests as representatives of the holders of their common equity, may take risks or otherwise act in ways that do not serve our interests as debt investors. Due to the lack of liquidity of the investments that NMG LLC typically holds in our portfolio companies, it may not be able to dispose of our investments in the event that we disagree with the actions of a portfolio company as readily

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as we would otherwise like to or at favorable prices which could decrease the value of our investments.

There has recently been a period of capital markets disruption which could occur again in the future.

          The U.S. capital markets have recently experienced extreme volatility and disruption, and these disruptive conditions could occur again in the future. Disruptions in the capital markets increased the spread between the yields realized on risk-free and higher risk securities, resulting in illiquidity in parts of the capital markets. A prolonged period of market illiquidity could have an adverse effect on our business, financial condition and results of operations. Unfavorable economic conditions could also increase NMG LLC's funding costs, limit New Mountain Guardian's and NMG LLC's access to the capital markets or result in a decision by lenders not to extend credit to NMG LLC. These events could limit our investment originations, limit our ability to grow and negatively impact our operating results.

Economic recessions or downturns could impair our portfolio companies and harm our operating results.

          Many of our portfolio companies may be susceptible to economic slowdowns or recessions and may be unable to repay our debt investments during these periods. Therefore, NMG LLC's non-performing assets are likely to increase, and the value of our portfolio is likely to decrease during these periods. Adverse economic conditions also may decrease the value of collateral securing some of our debt investments and the value of our equity investments. Economic slowdowns or recessions could lead to financial losses in our portfolio and a decrease in revenues, net income and assets. Unfavorable economic conditions also could increase NMG LLC's funding costs, limit New Mountain Guardian's and NMG LLC's access to the capital markets or result in a decision by lenders not to extend credit to NMG LLC. These events could prevent NMG LLC from increasing investments and harm our operating results.

Defaults by our portfolio companies may harm our operating results.

          A portfolio company's failure to satisfy financial or operating covenants imposed by NMG LLC or other lenders could lead to defaults and, potentially, termination of its loans and foreclosure on its secured assets, which could trigger cross-defaults under other agreements and jeopardize a portfolio company's ability to meet its obligations under the debt or equity securities that NMG LLC holds.

          NMG LLC may incur expenses to the extent necessary to seek recovery upon default or to negotiate new terms, which may include the waiver of certain financial covenants, with a defaulting portfolio company. In addition, lenders in certain cases can be subject to lender liability claims for actions taken by them when they become too involved in the borrower's business or exercise control over a borrower. It is possible that NMG LLC could become subject to a lender's liability claim, including as a result of actions taken if it renders significant managerial assistance to the borrower. Furthermore, if one of our portfolio companies were to file for bankruptcy protection, even though NMG LLC may have structured our investment as senior secured debt, depending on the facts and circumstances, including the extent to which NMG LLC provided managerial assistance to that portfolio company, a bankruptcy court might re-characterize our debt holding and subordinate all or a portion of NMG LLC's claim to claims of other creditors.

Changes in interest rates may affect NMG LLC's cost of capital and net investment income.

          To the extent NMG LLC borrows money to make investments, NMG LLC's net investment income will depend, in part, upon the difference between the rate at which it borrows funds and the rate at which it invests those funds. As a result, we can offer no assurance that a significant change in market interest rates will not have a material adverse effect on NMG LLC's net investment income in the event it uses debt to finance its investments. In periods of rising interest rates, NMG LLC's

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cost of funds would increase, which could reduce its net investment income. We expect that NMG LLC's long-term fixed-rate investments will be financed primarily with issuances of equity by New Mountain Guardian and long-term debt securities by NMG LLC. NMG LLC may use interest rate risk management techniques in an effort to limit its exposure to interest rate fluctuations. These techniques may include various interest rate hedging activities to the extent permitted by the 1940 Act.

We may not realize gains from our equity investments.

          When NMG LLC invests in Target Securities, it may acquire warrants or other equity securities of portfolio companies as well. NMG LLC may also invest in equity securities directly. To the extent NMG LLC holds equity investments, it will attempt to dispose of them and realize gains upon its disposition of them. However, the equity interests NMG LLC receives may not appreciate in value and, in fact, may decline in value. As a result, we may not be able to realize gains from our equity interests, and any gains that we do realize on the disposition of any equity interests may not be sufficient to offset any other losses we experience. We also may be unable to realize any value if a portfolio company does not have a liquidity event, such as a sale of the business, recapitalization or public offering, which would allow us to sell the underlying equity interests.

The performance of our portfolio companies may differ from our historical performance as our investment strategy will include primary originations in addition to secondary market purchases.

          Historically, our investment strategy consisted primarily of secondary market purchases in debt securities. We are currently in the process of adjusting our investment strategy to also include primary originations. While loans we originate and loans we purchase in the secondary market face many of the same risks associated with the financing of leveraged companies, we may be exposed to different risks depending on specific business considerations for secondary market purchases or origination of loans. As a result, this strategy may result in different returns from these investments that the types of returns we have historically experienced from secondary market purchases of debt securities.

We may be subject to additional risks if we invest in foreign securities and/or engage in hedging transactions.

          The 1940 Act generally requires that 70% of our investments be in issuers each of whom is organized under the laws of, and has its principal place of business in, any state of the United States, the District of Columbia, Puerto Rico, the Virgin Islands or any other possession of the United States. Our investment strategy does not presently contemplate investments in securities of non-U.S. companies. However, we may desire to make such investments in the future, to the extent that such transactions and investments are permitted under the 1940 Act. We expect that these investments would focus on the same types of investments that we make in U.S. middle-market companies and accordingly would be complementary to our overall strategy and enhance the diversity of our holdings. Investing in foreign companies could expose us to additional risks not typically associated with investing in U.S. companies. These risks include changes in exchange control regulations, political and social instability, expropriation, imposition of foreign taxes, less liquid markets and less available information than is generally the case in the United States, higher transaction costs, less government supervision of exchanges, brokers and issuers, less developed bankruptcy laws, difficulty in enforcing contractual obligations, lack of uniform accounting and auditing standards and greater price volatility. Investments denominated in foreign currencies would be subject to the risk that the value of a particular currency will change in relation to one or more other currencies. Among the factors that may affect currency values are trade balances, the level of short-term interest rates, differences in relative values of similar assets in different currencies, long-term opportunities for investment and capital appreciation and political developments. NMG LLC may employ hedging techniques to minimize these risks, but we can offer no assurance that it will, in fact, hedge currency risk, or that if it does, such strategies will be effective.

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          Engaging in hedging transactions would also, indirectly, entail additional risks to New Mountain Guardian stockholders. NMG LLC could, for example, use instruments such as interest rate swaps, caps, collars and floors and, if it were to invest in foreign securities, it could use instruments such as forward contracts or currency options and borrow under a credit facility in currencies selected to minimize our foreign currency exposure. In each such case, NMG LLC generally would seek to hedge against fluctuations of the relative values of our portfolio positions from changes in market interest rates or currency exchange rates. Hedging against a decline in the values of our portfolio positions would not eliminate the possibility of fluctuations in the values of such positions or prevent losses if the values of the positions declined. However, such hedging could establish other positions designed to gain from those same developments, thereby offsetting the decline in the value of such portfolio positions. These hedging transactions could also limit the opportunity for gain if the values of the underlying portfolio positions increased. Moreover, it might not be possible to hedge against an exchange rate or interest rate fluctuation that was so generally anticipated that NMG LLC would not be able to enter into a hedging transaction at an acceptable price.

          While NMG LLC may enter into these types of transactions to seek to reduce currency exchange rate and interest rate risks, unanticipated changes in currency exchange rates or interest rates could result in poorer overall investment performance than if it had not engaged in any such hedging transactions. In addition, the degree of correlation between price movements of the instruments used in a hedging strategy and price movements in the portfolio positions being hedged could vary. Moreover, for a variety of reasons, NMG LLC might not seek to establish a perfect correlation between the hedging instruments and the portfolio holdings being hedged. Any imperfect correlation could prevent NMG LLC from achieving the intended hedge and expose it and New Mountain Guardian to risk of loss. In addition, it might not be possible to hedge fully or perfectly against currency fluctuations affecting the value of securities denominated in non-U.S. currencies because the value of those securities would likely fluctuate as a result of factors not related to currency fluctuations.

Risks Relating to Our Corporate Structure

New Mountain Guardian will be a holding company with no direct operations of its own, and will depend on distributions from NMG LLC to meet its ongoing obligations.

          New Mountain Guardian will be a holding company with no direct operations of its own, and its only business and sole asset will be its direct ownership of common membership units of NMG LLC. As a result, all investment decisions relating to our portfolio will be made by the Investment Advisor under the supervision of NMG LLC's board of directors, which may be different from New Mountain Guardian's board of directors. Although NMG LLC's limited liability company agreement, or the "LLC Agreement", provides that all matters subject to a member vote will be voted on a "pass through" basis, including with respect to the election of NMG LLC's directors, New Mountain Guardian will not, and you, indirectly, as stockholders of New Mountain Guardian will not, have any control over NMG LLC's day-to-day operations and investment decisions.

          New Mountain Guardian also will not have any independent ability to generate revenue, and its only source of cash flow from operations will be distributions from NMG LLC. Consequently, New Mountain Guardian will rely on NMG LLC to cover the expenses of its day-to-day business, including expenses incident to New Mountain Guardian's status as a public company. Pursuant to the Administration Agreement, NMG LLC will reimburse the Administrator for New Mountain Guardian's allocable portion of overhead and other expenses incurred by the Administrator in performing its obligations to New Mountain Guardian under the Administration Agreement. However, if NMG LLC cannot or does not make the payments required pursuant to the Administration Agreement, New Mountain Guardian may be unable to cover these expenses.

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          In addition, because New Mountain Guardian is a holding company, its ability to pay distributions to its stockholders will depend on the prior distribution from NMG LLC of cash in an amount sufficient to pay quarterly distributions and to obtain and maintain its status as a RIC. The distribution of cash flows by NMG LLC to New Mountain Guardian will be subject to statutory restrictions under the Delaware Limited Liability Company Act, the 1940 Act and contractual restrictions under NMG LLC's debt instruments that may limit NMG LLC ability to make distributions. In addition, any distributions and payments of fees or costs will be based upon NMG LLC's financial performance. Any distributions of cash will be made on a pro rata basis to all of NMG LLC's members, including New Mountain Guardian and Guardian AIV, indirectly, through Guardian AIV Holdings, in accordance with each holders' respective percentage interest.

          Circumstances may arise in the future when the interests of NMG LLC's members conflict with the interests of New Mountain Guardian's stockholders. As a member of NMG LLC, New Mountain Guardian may owe fiduciary duties to the other members of NMG LLC that could conflict with fiduciary duties New Mountain Guardian's officers and directors owe to its stockholders. In addition, following the completion of this offering, NMG LLC's board of directors and the board of directors of New Mountain Guardian will be comprised of the same members. However, NMG LLC's board of directors will owe fiduciary duties to its members that could conflict with the fiduciary duties New Mountain Guardian's board of directors owes to its stockholders.

New Mountain or its affiliates may have interests that differ from your interests as stockholders.

          Following the completion of this offering and based on the mid-point of the range set forth on the cover of this prospectus, Guardian AIV will indirectly own, through Guardian AIV Holdings, approximately         % of the common membership units of NMG LLC and Guardian Partners will own approximately          % of New Mountain Guardian's outstanding common stock (assuming no exercise of the underwriters' option to purchase additional shares). New Mountain's interests, and the interests of the partners in Guardian AIV and Guardian Partners, may differ from your interests as stockholders.

          In addition, if Guardian AIV owns any common membership units, directly or indirectly, NMG LLC will generally be prohibited from making tax elections or taking positions on tax issues that it knows or would reasonably be expected to know would harm Guardian AIV Holdings, Guardian AIV or its partners than if such election or position had not been made or taken. See "Formation Transactions and Related Agreements — Structure-Related Agreements — NMG LLC Agreement".

Any future exchange by Guardian AIV Holdings of common membership units of NMG LLC for shares of New Mountain Guardian's common stock would significantly dilute your voting power with respect to the election of New Mountain Guardian directors or other matters that require the approval of New Mountain Guardian stockholders only. In addition, the interests of the partners of Guardian AIV following such exchange by Guardian AIV Holdings may be adverse to your interests as stockholders and could limit your ability to influence the outcome of key transactions, including any change of control.

          Pursuant to the terms of the LLC Agreement, Guardian AIV Holdings will have the right to exchange its common membership units for shares of New Mountain Guardian's common stock on a one-for-one basis. Following the completion of transactions described in this prospectus, Guardian AIV will indirectly own through Guardian AIV Holdings approximately         % of the common membership units of NMG LLC, or approximately         % of the common membership units of NMG LLC if the underwriters exercise their option to purchase additional shares in full. If Guardian AIV Holdings exercised its exchange rights with respect to a significant number of

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common membership units, the voting power of New Mountain Guardian's stockholders would be significantly diluted. As a result, Guardian AIV, indirectly through Guardian AIV Holdings, together with Guardian Partners would retain significant influence over decisions that require the approval of New Mountain Guardian's stockholders exclusively (such as the election of its directors and the approval of mergers or other significant corporate transactions) regardless of whether or not New Mountain Guardian's other stockholders believe that such decisions are in New Mountain Guardian's own best interests. If, following this offering, Guardian AIV Holdings exercised its exchange rights in full, Guardian AIV, indirectly through Guardian AIV Holdings, and Guardian Partners would own approximately         % and         % respectively of all outstanding shares of New Mountain Guardian's common stock, or approximately         % and         %, respectively, if the underwriters exercised their option to purchase additional shares in full. However, these entities would not exercise voting control over their shares of common stock because the right to vote those shares would be passed through to the partners of these entities. These investors may have interests that differ from your interests, and they may vote in a way with which you disagree and that may be adverse to your interests as stockholders. The concentration of ownership of New Mountain Guardian's common stock following the exercise of Guardian AIV Holdings' exchange right may also have the effect of delaying, preventing or deterring a change of control of New Mountain Guardian, could deprive New Mountain Guardian's stockholders of an opportunity to receive a premium for their common stock as part of a sale of New Mountain Guardian and may adversely affect the market price of New Mountain Guardian's common stock.

Risks Relating to this Offering and Our Common Stock

NMG LLC may be unable to invest a significant portion of the proceeds of this offering on acceptable terms in the timeframe contemplated by this prospectus.

          New Mountain Guardian will use the gross proceeds from this offering and the concurrent private placement to purchase, on a one-for-one basis, common membership units of NMG LLC. NMG LLC will, in turn, use these proceeds, after paying underwriting discounts and commissions and offering expenses, to make new investments in portfolio companies in accordance with our investment objective and strategies described in this prospectus. Delays in NMG LLC investing the net proceeds of this offering may cause our performance to be worse than that of other fully invested business development companies or other lenders or investors pursuing comparable investment strategies. We cannot assure you that NMG LLC will be able to identify any investments that meet our investment objective or that any investment that NMG LLC identifies will produce a positive return. NMG LLC may be unable to invest the net proceeds of this offering on acceptable terms within the time period that we anticipate or at all, which could harm our financial condition and operating results.

          We anticipate that, depending on market conditions, it may take up to six to twelve months to invest substantially all of the net proceeds of this offering in investments meeting our investment objective. During this period, NMG LLC will invest the net proceeds of this offering primarily in cash, cash equivalents, U.S. government securities, repurchase agreements and other high-quality investments maturing in one year or less from the time of investment, which may produce returns that are significantly lower than the returns which it expects to achieve when our portfolio is fully invested in securities meeting our investment objective. In addition, NMG LLC may also use the net proceeds to temporarily repay indebtedness (which amounts will be subject to reborrowing). As a result, any distributions that New Mountain Guardian receives from NMG LLC and pays to its stockholders during this period may be substantially lower than the distributions that it may be able to pay when our portfolio is fully invested in securities meeting our investment objective. In addition, until such time as the net proceeds of this offering are invested in securities meeting our investment objective, the market price for New Mountain Guardian's common stock may decline. Thus, the

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initial return on your investment may be lower than when, if ever, our portfolio is fully invested in securities meeting our investment objective.

The market price of New Mountain Guardian's common stock may fluctuate significantly.

          The market price and liquidity of the market for shares of New Mountain Guardian's common stock may be significantly affected by numerous factors, some of which are beyond our control and may not be directly related to our operating performance. These factors include:

•

price and volume fluctuations in the overall stock market or in the market for business development companies from time to time;



•

investor demand for shares of New Mountain Guardian's common stock;



•

significant volatility in the market price and trading volume of securities of registered closed-end management investment companies, business development companies or other financial services companies, which is not necessarily related to the operating performance of these companies;



•

the inability to raise equity capital;



•

NMG LLC's inability to borrow money or deploy or invest our capital;



•

fluctuations in interest rates;



•

any shortfall in revenue or net income or any increase in losses from levels expected by investors or securities analysts;



•

operating performance of companies comparable to us;



•

changes in regulatory policies or tax guidelines with respect to RICs or business development companies;



•

New Mountain Guardian's or NMG LLC's loss of status as or ability to operate as a business development company;



•

New Mountain Guardian's failure to qualify as a RIC, loss of RIC status or ability operate as a RIC;



•

actual or anticipated changes in NMG LLC's earnings or fluctuations in its operating results;



•

changes in the value of our portfolio of investments;



•

general economic conditions, trends and other external factors;



•

departures of key personnel; or



•

loss of a major source of funding.

Investing in New Mountain Guardian's common stock may involve an above average degree of risk.

          The investments NMG LLC may make may result in a higher amount of risk, volatility or loss of principal than alternative investment options. These investments in portfolio companies may be highly speculative and aggressive, and therefore, an investment in New Mountain Guardian's common stock may not be suitable for investors with lower risk tolerance.

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Prior to this offering, there has been no public market for New Mountain Guardian's common stock, and we cannot assure you that the market price of New Mountain Guardian's common stock will not decline following the offering.

          Prior to this offering, there has been no public market for New Mountain Guardian's common stock, and we cannot assure you that a trading market will develop or be sustained for New Mountain Guardian's common stock after this offering. The initial public offering price of New Mountain Guardian's common stock will be determined through negotiations among New Mountain Guardian and the underwriters and may not bear any relationship to the market price at which it will trade after this offering. Shares of closed-end management investment companies offered in an initial public offering often trade at a discount to the initial offering price due to sales loads, underwriting discounts and related offering expenses. In addition, shares of closed-end management investment companies have in the past frequently traded at discounts to their net asset values and New Mountain Guardian's stock may also be discounted in the market. This characteristic of closed-end management investment companies is separate and distinct from the risk that New Mountain Guardian's net asset value per share may decline. We cannot predict whether shares of New Mountain Guardian's common stock will trade above, at or below its net asset value per share. The risk of loss associated with this characteristic of closed-end management investment companies may be greater for investors expecting to sell shares of New Mountain Guardian's common stock purchased in this offering soon after the offering. In addition, if New Mountain Guardian's common stock trades below its net asset value per share, New Mountain Guardian will generally not be able to sell additional shares of its common stock to the public at its market price without first obtaining the approval of its stockholders (including its unaffiliated stockholders) and its independent directors for such issuance. Initially, the market for New Mountain Guardian's common stock will be extremely limited. Following this offering, sales of substantial amounts of New Mountain Guardian's common stock or the availability of such shares for sale, could adversely affect the prevailing market prices for its common stock.

We have not identified specific investments in which NMG LLC will invest the proceeds of this offering.

          As of the date of this prospectus, there are no definitive agreements for any specific investments in which NMG LLC will invest the net proceeds of this offering after such proceeds are contributed by New Mountain Guardian in exchange for common membership units of NMG LLC. Although we are and will continue to evaluate and seek new investment opportunities, you will not be able to evaluate prior to your purchase of common stock in this offering the manner in which NMG LLC will invest the net proceeds of this offering, or the economic merits of any new investment.

Investors in this offering may incur dilution.

          Upon completion of the formation transactions, New Mountain Guardian's as adjusted net asset value as of March 31, 2010 would have been approximately $             , or $             per share, on a fully diluted basis, assuming the conversion of all of the then outstanding common membership units of NMG LLC into a corresponding number of shares of New Mountain Guardian's common stock. After giving effect to (i) the completion of the formation transactions and the concurrent private placement, (ii) the sale of                          shares of New Mountain Guardian's common stock in this offering at an assumed initial public offering price of $             per share (the mid-point of the range set forth on the cover of this prospectus), after deducting underwriting discounts and commissions and estimated offering expenses payable by NMG LLC, (iii) the temporary repayment of indebtedness under NMG LLC's credit facility and (iv) the assumption that all of Guardian AIV Holdings' common membership units of NMG LLC were immediately exchanged

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for the corresponding number of shares of New Mountain Guardian's common stock, New Mountain Guardian's as adjusted net asset value as of March 31, 2010 would have been approximately $              million, or $             per share, on a fully diluted basis, representing an immediate decrease in its net asset value of $             per share. The foregoing assumes no exercise of the underwriters' option to purchase additional shares. If the underwriters' option to purchase additional shares is exercised in full, the as adjusted net asset value per share of New Mountain Guardian's common stock after this offering would be $             and the dilution per share to investors in this offering would be $             , in each case on a fully diluted basis. In addition, using the                          , 2010 estimated net asset value of $             and the same assumptions discussed above, New Mountain Guardian's pro forma net asset value is expected to be approximately $             per share, resulting in dilution to investors in this offering in New Mountain Guardian of $             per share, on a fully diluted basis.

Sales of substantial amounts of New Mountain Guardian's common stock in the public market may have an adverse effect on the market price of its common stock.

          Sales of substantial amounts of New Mountain Guardian's common stock, including by itself directly, Guardian Partners or Guardian AIV Holdings, if it exercises its right to exchange its common membership units of NMG LLC for shares of New Mountain Guardian's common stock on a one-for-one basis, or the perception that such sales could occur, could materially adversely affect the prevailing market prices for New Mountain Guardian's common stock. Guardian AIV Holdings and Guardian Partners currently intend to sell their interest in our business as soon as practicable from time to time, depending on market conditions and any applicable contractual or legal restrictions. In connection with this offering, Guardian AIV Holdings entered into a lock-up agreement that prevents the exchange of its common membership units of NMG LLC, and Guardian Partners has entered into a similar lock-up agreement that prevents the sale of New Mountain Guardian's common stock held by Guardian Partners, for up to 180 days after the date of this prospectus, subject to carve outs and an extension in certain circumstances as set forth in "Underwriting". Following the expiration of the lock-up, or earlier upon the consent of Goldman, Sachs & Co. and Wells Fargo Securities, LLC, Guardian AIV Holdings, Guardian Partners and the Investment Advisor, if applicable with respect to any common membership units received as payment of the incentive fee, will have the right, subject to certain conditions, to require New Mountain Guardian to register under the federal securities laws the sale of any shares of New Mountain Guardian's common stock held by them or that may be issued to and held by them upon exercise by Guardian AIV Holdings of the exchange right.

          In addition, New Mountain Guardian has granted Guardian AIV Holdings, Guardian Partners, the Investment Advisor, if applicable with respect to any common membership units received as payment of the incentive fee, and their permitted transferees certain "piggyback" registration rights which will allow them to include their shares in any future registrations of New Mountain Guardian equity securities, whether or not that registration relates to a primary offering by us or a secondary offering by or on behalf of any of New Mountain Guardian's stockholders. In particular, Guardian AIV Holdings, Guardian Partners and the Investment Advisor, if applicable with respect to any common membership units received as payment of the incentive fee, will have priority over New Mountain Guardian and any other of its stockholders in any registration that is an underwritten offering. See "Formation Transactions and Related Agreements — Structure Related Agreements — Registration Rights Agreement". Any such filing or the perception that such a filing may occur, could cause the prevailing market price of New Mountain Guardian's common stock to decline and may impact New Mountain Guardian's ability to sell equity to finance our operations. If substantial amounts of New Mountain Guardian's common stock were sold, this could impair its ability to raise additional capital through the sale of securities should New Mountain Guardian desire to do so.

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Certain provisions of New Mountain Guardian's certificate of incorporation and bylaws, the Delaware General Corporation Law as well as other aspects of our structure, including Guardian AIV's substantial interest in NMG LLC and Guardian Partners' ownership in New Mountain Guardian, could deter takeover attempts and have an adverse impact on the price of New Mountain Guardian's common stock.

          New Mountain Guardian's certificate of incorporation and bylaws as well as the Delaware General Corporation Law contain provisions that may have the effect of discouraging a third party from making an acquisition proposal for us. Among other things, New Mountain Guardian's certificate of incorporation and bylaws:

•

provide for a classified board of directors, which may delay the ability of New Mountain Guardian's stockholders to change the membership of a majority of its board of directors;



•

authorize the issuance of "blank check" preferred stock that could be issued by New Mountain Guardian's board of directors to thwart a takeover attempt;



•

do not provide for cumulative voting;



•

provide that vacancies on the board of directors, including newly created directorships, may be filled only by a majority vote of directors then in office;



•

limit the calling of special meetings of stockholders;



•

provide that New Mountain Guardian's directors may be removed only for cause;



•

require supermajority voting to effect certain amendments to New Mountain Guardian's certificate of incorporation and bylaws; and



•

require stockholders to provide advance notice of new business proposals and director nominations under specific procedures.

These anti-takeover provisions may inhibit a change in control in circumstances that could give the holders of New Mountain Guardian's common stock the opportunity to realize a premium over the market price for its common stock. The credit facility also includes covenants that, among other things, restrict its ability to dispose of assets, incur additional indebtedness, make restricted payments, create liens on assets, make investments, make acquisitions and engage in mergers or consolidations. The credit facility also includes change of control provisions that accelerate the indebtedness under the facility in the event of certain change of control events. In addition, certain aspects of our structure, including Guardian AIV's substantial interest in NMG LLC and Guardian Partners' ownership in New Mountain Guardian, may have the effect of discouraging a third party from making an acquisition proposal for New Mountain Guardian.

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SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

          This prospectus contains forward-looking statements that involve substantial risks and uncertainties. You can identify these statements by forward-looking words such as "anticipate", "believe", "could", "estimate", "expect", "intend", "may", "plan", "potential", "should", "will", "would" or similar words. You should read statements that contain these words carefully because they discuss our plans, strategies, prospects and expectations concerning our business, operating results, financial condition and other similar matters. We believe that it is important to communicate our future expectations to our investors. Our forward-looking statements include, but are not limited to, information in this prospectus regarding general domestic and global economic conditions, our structure, NMG LLC's future financing plans, New Mountain Guardian's and NMG LLC's ability to operate as business development companies and the expected performance of, and the yield on, our portfolio companies. In particular, there are forward-looking statements under "Prospectus Summary — The Company", "Business" and "Management's Discussion and Analysis of Financial Condition and Results of Operations". There may be events in the future, however, that we are not able to predict accurately or control. The factors listed under "Risk Factors", as well as any cautionary language in this prospectus, provide examples of risks, uncertainties and events that may cause our actual results to differ materially from the expectations we describe in our forward-looking statements. Before you invest in New Mountain Guardian's common stock, you should be aware that the occurrence of the events described in these risk factors and elsewhere in this prospectus could have a material adverse effect on our business, results of operation and financial position. Any forward-looking statement made by us in this prospectus speaks only as of the date on which we make it. Factors or events that could cause our actual results to differ may emerge from time to time, and it is not possible for us to predict all of them. We undertake no obligation to update or revise publicly any forward-looking statements, whether as a result of new information, future events or otherwise, except as required by law.

          The following factors are among those that may cause actual results to differ materially from our forward-looking statements:

•

New Mountain Guardian's and NMG LLC's future operating results;



•

the impact of a protracted decline in the liquidity of credit markets;



•

the general economy, including interest and inflation rates, and its impact on the industries in which NMG LLC invests;



•

New Mountain Guardian's and NMG LLC's business prospects and the prospects of our portfolio companies;



•

the impact of the formation transactions;



•

changes in New Mountain Guardian's and NMG LLC's expenses that we will incur as a stand-alone public company as compared to expectations;



•

the operating performance of companies comparable to us;



•

the impact of the investments that we expect NMG LLC to make;



•

the ability of our portfolio companies to achieve their objectives;



•

NMG LLC's ability to make investments consistent with our investment objectives, including with respect to the size, nature and terms of our investments;



•

the ability of the Investment Advisor to locate suitable investments for NMG LLC and to monitor and administer our investments;

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•

the ability of the Investment Advisor or its affiliates to attract and retain highly talented professionals;



•

NMG LLC's expected financings and investments;



•

New Mountain Guardian's and NMG LLC's regulatory structure and tax status;



•

New Mountain Guardian's and NMG LLC's loss of status or ability to operate as business development companies;



•

New Mountain Guardian's failure to qualify as a RIC, loss of RIC status or ability to operate as a RIC;



•

the adequacy of NMG LLC's cash resources and working capital and its anticipated use of proceeds;



•

the timing of cash flows, if any, from the operations of our portfolio companies;



•

the impact of interest rate volatility on our results, particularly to the extent NMG LLC uses leverage as part of our investment strategy;



•

actual and potential conflicts of interest with the Investment Advisor and other affiliates of New Mountain;



•

the impact of New Mountain Guardian's ownership of a minority of the outstanding common membership units of NMG LLC, New Mountain Guardian's only asset;



•

the timing, form and amount of any dividend distributions to New Mountain Guardian's stockholders and distributions from NMG LLC;



•

New Mountain Guardian's and NMG LLC's contractual arrangements and relationships with third parties;



•

the impact of future changes in laws or regulations and conditions in our operating areas; and



•

other factors, including those discussed in "Risk Factors".

          The forward-looking statements and projections contained in this prospectus are excluded from the safe harbor protection provided by Section 27A of the Securities Act.

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FORMATION TRANSACTIONS AND RELATED AGREEMENTS

Our History and Current Structure

          New Mountain Guardian was incorporated in Delaware on June 29, 2010. Prior to this offering, it did not engage in any activities, except in preparation for this offering, and it had no operations or assets. New Mountain currently owns the only issued and outstanding share of common stock of New Mountain Guardian. NMG LLC was formed as a subsidiary of Guardian AIV by New Mountain in October 2008. Guardian AIV was formed through an allocation of approximately $300 million of the $5.1 billion of commitments supporting Fund III, a private equity fund managed by New Mountain, and in February 2009 New Mountain formed a co-investment vehicle, Guardian Partners, comprising $20 million of commitments.

          The simplified diagram below depicts our current organizational structure prior to the formation transactions contemplated by this offering:

Holding Company Structure

General

          Following the completion of this offering and the transactions described in this prospectus, New Mountain Guardian will be a holding company with no direct operations of its own, and its only business and sole asset will be its ownership of common membership units of NMG LLC and it will have no material long-term liabilities. New Mountain Guardian's only source of cash flow from operations will be distributions from NMG LLC. NMG LLC will be New Mountain Guardian's operating entity and will be an externally managed finance company which will own all of the existing assets, and will have assumed all of the existing liabilities, of the Guardian Entities following this offering.

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Formation Transactions

          The following transactions have occurred or will occur in advance of the completion of this offering to effect our holding company structure:

•

Guardian AIV will cause its indirect, wholly-owned subsidiary, New Mountain Guardian Debt Funding, L.L.C., to merge with and into NMG LLC, Guardian AIV's direct, wholly-owned subsidiary, with NMG LLC as the surviving company.



•

Guardian Partners will contribute to its indirect, wholly-owned subsidiary, New Mountain Guardian Partners Debt Funding, L.L.C., all of the assets held directly by Guardian Partners, and then Guardian Partners will cause New Mountain Guardian Partners Debt Funding, L.L.C. to merge with and into NMG LLC, with NMG LLC as the surviving company. Guardian Partners will receive an interest in NMG LLC as consideration for the transfer of assets in the merger.



•

Guardian AIV and Guardian Partners will enter into an amended and restated limited liability company agreement of NMG LLC pursuant to which their respective membership interests in NMG LLC will be reclassified into common membership units.



•

Guardian AIV will contribute to Guardian AIV Holdings, a newly formed Delaware corporation, its common membership units of NMG LLC in exchange for common stock of Guardian AIV Holdings.



•

Guardian AIV Holdings will enter into an amended limited liability company agreement of NMG LLC, pursuant to which Guardian AIV Holdings will be admitted as a member of NMG LLC.



•

Guardian Partners will contribute to New Mountain Guardian its common membership units of NMG LLC in exchange for shares of New Mountain Guardian's common stock.



•

New Mountain Guardian will enter into the Acquisition Agreement with NMG LLC, pursuant to which it will acquire from NMG LLC a number of common membership units of NMG LLC equal to the number of shares of common stock sold by New Mountain Guardian in this offering and the concurrent private placement at a purchase price per unit equal to the per share offering price at which New Mountain Guardian's common stock is sold pursuant to this offering.



•

New Mountain Guardian and NMG LLC will enter into the Administration Agreement and NMG LLC will enter into the Investment Management Agreement effective upon the closing of this offering.



•

New Mountain Guardian, NMG LLC and Guardian AIV Holdings will elect to be treated as business development companies under the 1940 Act.



•

New Mountain Guardian and Guardian AIV Holdings will enter into an amended and restated limited liability company agreement of NMG LLC, pursuant to which New Mountain Guardian will be admitted as a member of NMG LLC and NMG LLC will split the number of outstanding common membership units so that a one-to-one ratio can be maintained between the number of common membership units held by New Mountain Guardian and the number of shares of New Mountain Guardian's common stock outstanding following the completion of this offering.

          Prior to this offering, NMG LLC will calculate net asset value per unit of NMG LLC, the "cutoff NAV", as of                    , 2010, the "cutoff date". The cutoff NAV will be determined and approved by NMG LLC's board of directors and will be calculated consistent with its policies for determining net asset value. See "Determination of Net Asset Value". Consistent with these policies, an

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independent third party valuation firm will provide NMG LLC with valuation assistance with respect to each investment for which market quotations are not available. NMG LLC will accrue interest income and related expenses as of the cutoff date. The cutoff NAV calculation will be comprised of all the investments at fair value plus any interest income accruals, less any expense accruals through the cutoff date. NMG LLC will not accept any contributions from, nor make any distributions to, the Guardian Entities' limited partners from the cutoff date through the date of this offering.

Consequences of this Offering and the Formation Transactions

          Upon completion of this offering, New Mountain Guardian will cancel the initial share of its common stock held by New Mountain for no consideration. Based on the mid-point of the range set forth on the cover of this prospectus, New Mountain Guardian will own approximately         % and Guardian AIV will indirectly own, through Guardian AIV Holdings, approximately         % of the common membership units of NMG LLC and Guardian Partners will own approximately         % of New Mountain Guardian's outstanding common stock, assuming no exercise of the underwriters' option to purchase additional shares. If the underwriters exercise their option to purchase additional shares of New Mountain Guardian's common stock, pursuant to the Acquisition Agreement, immediately thereafter New Mountain Guardian will acquire from NMG LLC an equivalent number of additional common membership units in exchange for the gross proceeds New Mountain Guardian receives upon exercise of this option.

          After completion of this offering, New Mountain Guardian's only business and sole asset will be its ownership of common membership units of NMG LLC, and it will have no material long-term liabilities. New Mountain Guardian's only source of cash flow from operations will be distributions from NMG LLC.

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          The simplified diagram below depicts our summarized organizational structure immediately after the transactions described in this prospectus (assuming no exercise of the underwriters' option to purchase additional shares):

*

These common membership units are exchangeable into shares of New Mountain Guardian common stock on a one-for-one basis.

Structure-Related Agreements

          In connection with the formation transactions referred to above and this offering, New Mountain Guardian and NMG LLC are entering into various agreements governing the relationship among New Mountain Guardian, Guardian AIV, Guardian Partners, Guardian AIV Holdings and NMG LLC.

          These agreements are summarized below, which summaries are qualified in their entirety by reference to the full text of the agreements which are filed as exhibits to the registration statement of which this prospectus is a part.

          For a description of the agreements governing the relationship between NMG LLC and the Investment Advisor and New Mountain Guardian's and NMG LLC's relationship with the Administrator, see "Investment Management Agreement" and "Administration Agreement".

Acquisition Agreement

          As set forth above, in connection with this offering, New Mountain Guardian will enter into the Acquisition Agreement with NMG LLC, pursuant to which it will purchase from NMG LLC, with the gross proceeds of this offering and the concurrent private placement,                     common membership units of NMG LLC (the number of common membership units will equal the number of shares of New Mountain Guardian's common stock sold in this offering and the concurrent private

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placement). New Mountain Guardian will also agree pursuant to the Acquisition Agreement, in the event the underwriters exercise their option to purchase additional shares of New Mountain Guardian's common stock, to purchase from NMG LLC a number of common membership units equal to the number of shares of New Mountain Guardian's common stock sold pursuant to this option. Assuming the underwriters exercise their option to purchase additional shares in full, New Mountain Guardian will use the gross proceeds from the closing of the option to pay for those units and will own approximately         % of the common membership units of NMG LLC. The per unit purchase price New Mountain Guardian will pay for the common membership units purchased pursuant to the Acquisition Agreement will be equal to the per share offering price at which New Mountain Guardian's common stock is sold pursuant to this offering.

NMG LLC Agreement

First Amended and Restated LLC Agreement

          Prior to the completion of this offering, Guardian AIV's and Guardian Partner's interest in NMG LLC will be reclassified into a new class of common membership units pursuant to a first amended and restated limited liability company agreement of NMG LLC. Although New Mountain Guardian will not be a member under this agreement, it will be a party to and third-party beneficiary of this agreement. This agreement will provide for an exchange right, whereby, upon appropriate notice, Guardian AIV, or its transferees, will have the right to exchange all or any portion of its common membership units for shares of New Mountain Guardian's common stock on a one-for-one basis. This right can be conditionally exercised by Guardian AIV, or its transferees, meaning that prior to the receipt of shares of New Mountain Guardian's common stock upon exchange, Guardian AIV, or its transferees, can withdraw its request to have its common membership units exchanged for shares of New Mountain Guardian's common stock.

          In addition, in connection with the contribution by Guardian AIV of its common membership units to Guardian AIV Holdings, NMG LLC's limited liability company agreement will be further amended to admit Guardian AIV Holdings as a member of NMG LLC.

Second Amended and Restated LLC Agreement

          In connection with this offering, New Mountain Guardian and Guardian AIV Holdings will enter into a second amended and restated limited liability company agreement of NMG LLC. We refer to this second amended and restated agreement as the "LLC Agreement". Limited liability company interests in NMG LLC may, to the extent permissible under the 1940 Act, be represented by one or more classes of units.

          New Mountain Guardian Business.    New Mountain Guardian will have no direct operations, and its only business and sole asset will be its ownership of common membership units of NMG LLC. Under the LLC Agreement, New Mountain Guardian will not be permitted to conduct any business or ventures other than in connection with:

•

the acquisition, ownership or disposition of its common membership units of NMG LLC; and



•

its operation as a public reporting company.

          Under the LLC Agreement, NMG LLC may conduct any business that may be lawfully conducted by a limited liability company under the Delaware Limited Liability Company Act, except that the LLC Agreement requires that NMG LLC conduct its operations in such a manner that will (1) permit New Mountain Guardian to satisfy the requirements for qualification as a business development company, (2) permit New Mountain Guardian to satisfy the requirements for qualification as a RIC for federal income tax purposes and (3) ensure that NMG LLC will not be classified as a "publicly traded partnership" for purposes of Section 7704 of the Code.

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          Board of Directors.    NMG LLC will be managed by a board of directors that will be elected by NMG LLC's members, voting on a "pass through" basis. As a result, the partners in Guardian AIV and New Mountain Guardian's stockholders, including the partners in Guardian Partners, will elect NMG LLC's board of directors. For a description of these "pass through" voting rights, see "— Voting". NMG LLC's initial board of directors will be comprised of the same individuals as the board of directors of New Mountain Guardian Corporation. Under the LLC Agreement, NMG LLC will be required to endeavor to nominate the same slate of director nominees for election by its members as New Mountain Guardian. However, there can be no assurance that NMG LLC's board composition and New Mountain Guardian's board composition will remain the same following the completion of this offering.

          Management.    Subject to the overall supervision of NMG LLC's board of directors, the Investment Advisor will manage NMG LLC's day-to-day operations and provide NMG LLC with investment management services pursuant to the Investment Management Agreement. NMG LLC will pay a management fee and incentive fee to the Investment Advisor for its services.

          Tax Matters.    New Mountain Guardian will be NMG LLC's tax matters member. If Guardian AIV owns any common membership units, directly or indirectly, NMG LLC will generally be prohibited from making tax elections or taking positions on tax issues that it knows or would reasonably be expected to know would harm Guardian AIV Holdings, Guardian AIV or its partners than if such election or position had not been made or taken. Guardian AIV Holdings will also have a consent right over New Mountain Guardian's actions as NMG LLC's tax matters member, including initiating proceedings and extending statutes of limitations, if such action would have a significant adverse effect on Guardian AIV Holdings, Guardian AIV or its partners. In addition, NMG LLC must operate substantially all of its business directly or, subject to compliance with applicable law, through entities treated as partnerships or disregarded entities for federal income tax purposes.

          Exchange Right.    The exchange right of Guardian AIV Holdings, as transferee of Guardian AIV, will be the same as set forth in the First Amended and Restated LLC Agreement. In addition, if New Mountain Guardian and NMG LLC receive exemptive relief to permit NMG LLC to pay 100%, on an after tax basis, of the incentive fee in common membership units of NMG LLC, any such common membership units received by the Investment Advisor will also be exchangeable for shares of New Mountain Guardian's common stock to the same extent as set forth in the First Amended and Restated LLC Agreement.

          Distributions and Allocations of Profits and Losses.    The LLC Agreement will provide that distributions of cash from NMG LLC will be determined by NMG LLC's board of directors and will be made pro rata among the members holding common membership units in accordance with their respective percentage interests in NMG LLC. NMG LLC intends to make distributions to NMG LLC's members that will be sufficient to enable New Mountain Guardian to pay quarterly distributions to its stockholders and to obtain and maintain its status as a RIC.

          Similarly, the LLC Agreement provides that, for tax purposes, subject to compliance with the provisions of Section 704(b) and 704(c) of the Code and the corresponding Treasury regulations, NMG LLC will allocate items of income, gain, loss, deduction and credit to its members, including New Mountain Guardian, pro rata in proportion to the number of outstanding common membership units of NMG LLC held by each such member. New Mountain Guardian's allocable share of NMG LLC's losses cannot be passed through to its stockholders but will be taken into account in determining New Mountain Guardian's taxable income that is required to be distributed to its stockholders by reason of New Mountain Guardian's status as a RIC.

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          If NMG LLC liquidates, debts and other obligations must be satisfied before the members may receive any distributions. Any distributions to members then will be made to members in accordance with their respective positive capital account balances.

          Capital Contributions.    Upon the completion of this offering, in connection with New Mountain Guardian's acquisition of common membership units of NMG LLC and pursuant to the Acquisition Agreement, New Mountain Guardian will contribute to NMG LLC the gross proceeds of this offering and the concurrent private placement as its initial capital contribution in exchange for                    common membership units, or                                        common membership units if the underwriters exercise their option to purchase additional shares in full. Following this initial capital contribution and the formation transactions described above and based on the mid-point of the range set forth on the cover of this prospectus, New Mountain Guardian will own approximately         % and Guardian AIV will indirectly own through Guardian AIV Holdings approximately         % of the common membership units of NMG LLC and Guardian Partners will own approximately         % of New Mountain Guardian's outstanding common stock, assuming no exercise of the underwriters' option to purchase additional shares.

          Under the LLC Agreement, New Mountain Guardian is also required to contribute the gross proceeds of any subsequent offering of its common stock by New Mountain Guardian as additional capital to NMG LLC in exchange for, on a one-to-one basis, additional common membership units of NMG LLC. See "— One-to-One Ratio" below. If New Mountain Guardian contributes additional capital to NMG LLC, it will receive additional common membership units of NMG LLC and its percentage interest in NMG LLC will be increased on a proportionate basis based upon the amount of such additional capital contributions. Conversely, the percentage interests of other members will be decreased on a proportionate basis in the event of additional capital contributions by New Mountain Guardian. In addition, if New Mountain Guardian contributes additional capital to NMG LLC, NMG LLC can revalue its property to its fair market value (as determined by its board of directors) and the capital accounts of the members will be adjusted to reflect the manner in which the unrealized gain or loss inherent in such property (that has not been reflected in the capital accounts previously) would be allocated among the members under the terms of the LLC Agreement if there were a taxable disposition of such property for its fair market value (as determined by its board of directors) on the date of revaluation. Under the LLC Agreement, New Mountain Guardian is also required to contribute to NMG LLC any reinvested distributions received by it pursuant to its dividend reinvestment plan. In addition, if New Mountain Guardian uses newly issued shares to implement the plan, it will receive, on a one-for-one basis, additional common membership units of NMG LLC in exchange for such reinvested distributions.

          One-to-One Ratio.    The LLC Agreement contains various provisions requiring that New Mountain Guardian and NMG LLC take certain actions in order to maintain, at all times, a one-to-one ratio between the number of common membership units held by New Mountain Guardian and the number of shares of New Mountain Guardian's common stock outstanding. This one-to-one ratio must also be maintained in the event that New Mountain Guardian issues additional shares of its common stock. Accordingly, every time New Mountain Guardian issues shares of its common stock, other than in connection with the exercise of the exchange right by Guardian AIV Holdings or the Investment Advisor, if applicable with respect to any common membership units received as payment of the incentive fee, NMG LLC will be required to issue additional common membership units to New Mountain Guardian. In addition, in order for New Mountain Guardian to pay a dividend or other distribution to holders of its common stock, it must be accompanied by a prior distribution by NMG LLC to all of its members.

          If New Mountain Guardian redeems, repurchases, acquires, exchanges, cancels or terminates any shares of its common stock, this action must be accompanied by an immediately prior identical (including with respect to the appropriate consideration paid for such action) redemption,

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repurchase, acquisition, exchange, cancellation or termination of the common membership units of NMG LLC held by New Mountain Guardian. If New Mountain Guardian splits its common stock, this action must be accompanied by an immediately prior identical split of common membership units of NMG LLC. In addition, in general, upon any consolidation or merger or combination to which New Mountain Guardian is a party or any sale or disposition of all or substantially all of its assets to a third party, New Mountain Guardian is required to take all necessary action so that the common membership units held by Guardian AIV Holdings and the Investment Advisor, if applicable with respect to any common membership units received as payment of the incentive fee, will be exchangeable on a per-common membership unit basis at any time or from time to time following such event into the kind and amount of shares of stock and/or other securities or property (including cash) receivable upon such event by holders of New Mountain Guardian's common stock.

          The LLC Agreement also provides that, in connection with any reclassification or recapitalization or any other distribution or dilutive or concentrative event by New Mountain Guardian, if Guardian AIV Holdings or the Investment Advisor, if applicable with respect to any common membership units received as payment of the incentive fee, exercises the exchange right following such event, Guardian AIV Holdings and, if applicable with respect to any common membership units received as payment of the incentive fee, the Investment Advisor will generally be treated as if they were entitled to receive the number of shares of New Mountain Guardian's common stock or other property (including cash) that it would have been entitled to receive had it exercised its exchange right immediately prior to the record date of such event. In addition, the LLC Agreement provides that New Mountain Guardian and NMG LLC must take all necessary action in order to maintain the one-to-one ratio if in the future New Mountain Guardian determines to issue options or other types of equity compensation to individuals that provide services to NMG LLC.

          Voting.    The LLC Agreement provides that all matters subject to a member vote under the LLC Agreement or Delaware law will be voted on a "pass through" basis. Accordingly, the partners in Guardian AIV and New Mountain Guardian's stockholders, including the partners in Guardian Partners, will vote on all such matters in accordance with their respective indirect percentage ownership in NMG LLC. Guardian AIV Holdings, Guardian AIV and Guardian Partners will not have any separate voting power other than to pass through the votes of the respective partners of Guardian AIV and Guardian Partners.

          Expenses.    All of NMG LLC's expenses and all of New Mountain Guardian's expenses, including any amounts owed pursuant to the Administration Agreement, will be borne by NMG LLC.

          Dissolution.    The LLC Agreement will provide that the unanimous consent of NMG LLC's members, voting on a "pass through" basis as described above, will be required to voluntarily dissolve NMG LLC. In addition to a voluntary dissolution, NMG LLC will be dissolved upon the entry of a decree of judicial dissolution in accordance with Delaware law. Upon a dissolution event, the proceeds of liquidation will be distributed in the following order:

•

first, to pay the expenses of winding up, liquidating and dissolving NMG LLC and all of its creditors, including members who are creditors; and



•

second, to the members pro rata in accordance with their respective positive capital account balances.

          Information.    The LLC Agreement provides that NMG LLC's members will be entitled to certain information regarding NMG LLC. This information includes quarterly and annual information regarding NMG LLC, information required for certain tax matters and any other information required under Delaware law or as reasonably requested by a member.

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          Confidentiality.    Each member will agree to maintain the confidentiality of any information received by the member or its affiliates and representatives in connection with the transactions contemplated by the LLC Agreement which is determined to be confidential for a period of three years following the earlier of the date of NMG LLC's dissolution or the date such member ceases to be a member, with customary exceptions, including to the extent disclosure is required by law or judicial process.

          Restrictions on Transfer.    The LLC Agreement provides that, subject to certain limited exceptions (including transfers to affiliates), a member may not transfer any of its common membership units of NMG LLC to any person without the consent of NMG LLC's board of directors, which consent may be given or withheld in their sole and absolute discretion. No member shall have the right to substitute a transferee as a member in its place. A transferee of common membership units of NMG LLC may be admitted as a substituted member only with the consent of NMG LLC's board of directors, which consent may be given or withheld in their sole and absolute discretion.

          Amendment.    Unless otherwise required by law, the LLC Agreement may be amended only by the written consent of each of the members; provided, however, that no amendment may be made without the consent of a member if the amendment would adversely affect the rights of the member other than on a pro rata basis with other members of common membership units.

          Indemnification.    The LLC Agreement provides for indemnification of NMG LLC's members, directors and officers and their respective subsidiaries or affiliates from and against liabilities arising out of or relating to NMG LLC's business, the LLC Agreement, any person's status as NMG LLC's member, director or officer or any action taken by any member, director or officer of NMG LLC under the LLC Agreement or otherwise on NMG LLC's behalf, except that no person entitled to indemnification under the LLC Agreement will be entitled to indemnification if the liability results from the gross negligence or willful misconduct of such person.

          Term.    NMG LLC shall continue until terminated as provided in the LLC Agreement or by operation of law.

          Fiduciary Duties.    Circumstances may arise in the future when the interests of NMG LLC's members conflict with the interests of New Mountain Guardian's stockholders. As a member of NMG LLC, New Mountain Guardian may owe fiduciary duties to the other members of NMG LLC that could conflict with fiduciary duties New Mountain Guardian's officers and directors owe to its stockholders. In addition, following the completion of this offering, NMG LLC's board of directors and the board of directors of New Mountain Guardian will be comprised of the same members. However, NMG LLC's board of directors will owe fiduciary duties to NMG LLC's members that could conflict with the fiduciary duties New Mountain Guardian's board of directors owes to New Mountain Guardian's stockholders.

Registration Rights Agreement

          In connection with this offering, New Mountain Guardian will enter into a registration rights agreement, or the Registration Rights Agreement, with Guardian AIV Holdings, Guardian Partners and the Investment Advisor. Subject to several exceptions, Guardian AIV Holdings, Guardian Partners and the Investment Advisor will have the right to require New Mountain Guardian to register for public resale under the Securities Act all registerable securities that are held by any of them and that they request to be registered at any time after the expiration or waiver of the lock-up period following this offering. Registerable securities subject to the Registration Rights Agreement are shares of New Mountain Guardian's common stock issued or issuable in exchange for common membership units and any other shares of New Mountain Guardian's common stock held by

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Guardian AIV Holdings, Guardian Partners, the Investment Advisor and any of their transferees. This right can be conditionally exercised by Guardian AIV Holdings, Guardian Partners or the Investment Advisor, meaning that prior to the registration of the shares Guardian AIV Holdings, Guardian Partners or the Investment Advisor can withdraw their request to have the shares registered. Guardian AIV Holdings, Guardian Partners and the Investment Advisor may each assign their rights to any person that acquires registerable securities subject to the Registration Rights Agreement and who agrees to be bound by the terms of the Registration Rights Agreement.

          Guardian AIV Holdings, Guardian Partners and the Investment Advisor may require New Mountain Guardian to use its best efforts to register under the Securities Act all or any portion of these registerable securities upon a "demand request". The demand registration rights are subject to certain limitations. New Mountain Guardian is not obligated to:

•

cause a registration statement with respect to a demand request to be declared effective within             days after the effective date of a previous demand registration, other than a shelf registration pursuant to Rule 415 under the Securities Act of 1933, or within 180 days after the effective date of the registration statement of which this prospectus is a part (unless the lock-up agreement entered into by Guardian AIV Holdings and Guardian Partners has been waived by the underwriters (see "Underwriting"));



•

cause a registration statement with respect to a demand request to be declared effective unless the demand request is for a number of shares with a market value that is equal to at least $              million; or



•

cause to be declared effective more than             registration statements with respect to demand registration rights.

The Registration Rights Agreement will include limited blackout and suspension periods. In addition, Guardian AIV Holdings, Guardian Partners and the Investment Advisor may also require New Mountain Guardian to file a shelf registration statement on Form N-2 for the resale of their registerable securities if New Mountain Guardian is eligible to use Form N-2 at that time.

          Holders of registerable securities will also have "piggyback" registration rights, which means that these holders may include their respective shares in any future registrations of New Mountain Guardian's equity securities, whether or not that registration relates to a primary offering by New Mountain Guardian or a secondary offering by or on behalf of any of New Mountain Guardian's stockholders. Guardian AIV Holdings, Guardian Partners and the Investment Advisor will have priority over New Mountain Guardian in any registration that is an underwritten offering.

          Guardian AIV Holdings, Guardian Partners and the Investment Advisor will be responsible for the expenses of any demand registration (including underwriters' discounts or commissions) and their pro rata share of any piggyback registration. Guardian AIV Holdings, Guardian Partners and the Investment Advisor have also agreed to indemnify New Mountain Guardian with respect to liabilities resulting from untrue statements or omissions furnished by them to New Mountain Guardian relating to Guardian AIV Holdings, Guardian Partners or the Investment Advisor in any registration statement.

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BUSINESS DEVELOPMENT COMPANY
AND REGULATED INVESTMENT COMPANY ELECTIONS

          In connection with this offering, New Mountain Guardian and NMG LLC intend to elect to be treated as business development companies under the 1940 Act prior to the completion of this offering. In addition, New Mountain Guardian intends to elect to be treated, and intends to qualify annually, as a RIC under Subchapter M of the Code, commencing with its taxable year ending on December 31, 2010. New Mountain Guardian's and NMG LLC's election to be treated as business development companies and New Mountain Guardian's election to be treated as a RIC will have a significant impact on our future operations. Some of the most important effects on our future operations of New Mountain Guardian's and NMG LLC's respective elections to be treated as business development companies and New Mountain Guardian's election to be treated as a RIC are outlined below. In connection with this offering and the intended elections to be treated as business development companies, New Mountain Guardian and NMG LLC expect to file a request with the SEC for exemptive relief to allow them to take certain actions that would otherwise be prohibited by the 1940 Act, as applicable to business development companies.

NMG LLC will report our investments at market value or fair value with changes in value reported through its statement of operations.

          In accordance with the requirements of Article 6 of Regulation S-X, NMG LLC will report all of our investments, including debt investments, at market value or, for investments that do not have a readily available market value, at their fair value as determined in good faith by NMG LLC's board of directors. Because New Mountain Guardian will be a holding company with no direct operations of its own, fair value determinations with respect to our investments will be made by NMG LLC's board of directors. Changes in these values will be reported through NMG LLC's statement of operations under the caption entitled "total net unrealized appreciation (depreciation) from investments". See "Determination of Net Asset Value".

New Mountain Guardian generally will be required to pay federal income taxes only on the portion of its taxable income that it does not distribute to its stockholders (actually or constructively).

          As a RIC, so long as New Mountain Guardian meets certain minimum distribution, source-of-income and asset diversification requirements, it generally will be required to pay federal income taxes only on the portion of its taxable income and gains that it does not distribute (actually or constructively) and certain built-in gains, if any. Because New Mountain Guardian will have no assets other than its ownership of common membership units of NMG LLC and no source of cash flow other than distributions from NMG LLC, New Mountain Guardian will look to NMG LLC's assets and income, and will rely on distributions made by NMG LLC to New Mountain Guardian, for purposes of satisfying these requirements. NMG LLC intends to conduct its operations and make distributions to its members in a manner that will enable New Mountain Guardian to satisfy these requirements.

NMG LLC's ability to use leverage as a means of financing our portfolio of investments will be limited.

          As a business development company, NMG LLC will be required to meet a coverage ratio of total assets, less liabilities and indebtedness not represented by senior securities, to total senior securities of at least 200%. For this purpose, senior securities include all borrowings and any preferred membership units NMG LLC may issue in the future. In addition to any limitations imposed by NMG LLC's existing or future credit facilities, NMG LLC's ability to continue to utilize

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leverage as a means of financing our portfolio of investments may also be limited by this asset coverage test. Because New Mountain Guardian will have no assets other than its ownership of common membership units of NMG LLC and will have no material long-term liabilities, New Mountain Guardian will look to NMG LLC's assets for purposes of satisfying this test.

New Mountain Guardian intends to distribute substantially all of its income to its stockholders.

          As a RIC, New Mountain Guardian intends to distribute to its stockholders substantially all of its annual taxable income, except that it may retain certain net capital gains for reinvestment in common membership units of NMG LLC. New Mountain Guardian may make deemed distributions to its stockholders of some or all of its retained net capital gains. If this happens, you will be treated as if you had received an actual distribution of the capital gains and reinvested the net after-tax proceeds in New Mountain Guardian. In general, you also would be eligible to claim a tax credit (or, in certain circumstances, obtain a tax refund) equal to your allocable share of the tax New Mountain Guardian paid on the deemed distribution. See "Material Federal Income Tax Considerations". NMG LLC intends to make distributions to its members that will be sufficient to enable New Mountain Guardian to obtain and maintain its status as a RIC.

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USE OF PROCEEDS

          We estimate that New Mountain Guardian will receive proceeds from the sale of the                                        shares of its common stock in this offering of approximately $             , or approximately $             if the underwriters exercise their option to purchase additional shares in full, in each case assuming an initial public offering price of $             per share (the mid-point of the range set forth on the cover of this prospectus). In connection with this offering, New Mountain Guardian will enter into the Acquisition Agreement with NMG LLC, pursuant to which New Mountain Guardian will purchase from NMG LLC                           common membership units of NMG LLC (the number of common membership units will equal the number of shares of New Mountain Guardian's common stock sold in this offering and the concurrent private placement). The per unit purchase price New Mountain Guardian will pay for the common membership units purchased pursuant to the Acquisition Agreement will be equal to the per share offering price at which New Mountain Guardian's common stock is sold pursuant to this offering. Accordingly, New Mountain Guardian will not retain any of the proceeds of this offering. If the underwriters exercise their option to purchase                          additional shares of New Mountain Guardian's common stock, New Mountain Guardian will use any proceeds from the exercise of this option to purchase additional common membership units of NMG LLC (the number of additional common membership units will equal the number of shares of New Mountain Guardian's common stock sold pursuant to this option). See "Formation Transactions and Related Agreements — Holding Company Structure" and "Underwriting".

          NMG LLC will use a portion of these proceeds to pay the underwriting discounts and commissions and estimated expenses of this offering, and intends to use the remaining net proceeds from this offering for new investments in portfolio companies in accordance with our investment objective and strategies described in this prospectus, to temporarily repay indebtedness (which will be subject to reborrowing), to pay New Mountain Guardian's and its operating expenses and distributions to its members and for general corporate purposes. Based on current market conditions, we anticipate that it may take up to six to twelve months for NMG LLC to fully invest the net proceeds it receives in connection with this offering. However, if market conditions change, it may take longer than twelve months to fully invest the net proceeds from this offering. We cannot assure you that we will achieve our targeted investment pace.

          Pending such use, NMG LLC will invest the net proceeds primarily in cash, cash equivalents, U.S. government securities and other high-quality investments that mature in one year or less from the date of investment. See "Regulation — Temporary Investments" for additional information about temporary investments NMG LLC may make while waiting to make longer-term investments in pursuit of our investment objective.

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DISTRIBUTIONS

          New Mountain Guardian intends to pay quarterly distributions to its stockholders out of assets legally available for distribution, beginning with its first full quarter after the completion of this offering. New Mountain Guardian's quarterly distributions, if any, will be determined by its board of directors. New Mountain Guardian's first quarterly distribution, which it expects will be payable in                          2010, is expected to be between $             and $             per share. The actual amount of such distribution, if any, remains subject to approval by New Mountain Guardian's board of directors, and there can be no assurance that any distribution paid will fall within such range. In addition, because New Mountain Guardian will be a holding company, it will only be able to pay distributions on its common stock from distributions received from NMG LLC. NMG LLC intends to make distributions to its members that will be sufficient to enable New Mountain Guardian to pay quarterly distributions to its stockholders and to obtain and maintain its status as a RIC. While it is intended that the distributions made by NMG LLC will be sufficient to enable New Mountain Guardian to pay quarterly distributions to its stockholders and to obtain and maintain its status as a RIC, there can be no assurances that the distributions from NMG LLC will be sufficient to pay distributions to New Mountain Guardian's stockholders in the future.

          New Mountain Guardian intends to elect to be treated, and intends to qualify annually, as a RIC under Subchapter M of the Code, commencing with its taxable year ending on December 31, 2010. To obtain and maintain RIC status, New Mountain Guardian must, among other things, distribute at least 90% of its net ordinary income and realized net short-term capital gains in excess of realized net long-term capital losses, if any. In order to avoid certain excise taxes imposed on RICs, New Mountain Guardian currently intends to distribute during each calendar year an amount at least equal to the sum of (1) 98% of its net ordinary income for the calendar year, (2) 98% of its capital gains in excess of capital losses for the one-year period ending on October 31 of the calendar year and (3) any net ordinary income and net capital gains for preceding years that were not distributed during such years. New Mountain Guardian may retain certain net capital gains (i.e., realized net long-term capital gains in excess of realized net short-term capital losses) for reinvestment in common membership units of NMG LLC and treat such amounts as deemed distributions to its stockholders. If New Mountain Guardian does this, you will be treated as if you had received an actual distribution of the capital gains New Mountain Guardian retained and then you reinvested the net after-tax proceeds in New Mountain Guardian's common stock. In general, you also will be eligible to claim a tax credit (or, in certain circumstances, obtain a tax refund) equal to your allocable share of the tax New Mountain Guardian paid on the capital gains deemed distributed to you. The distributions New Mountain Guardian pays to its stockholders in a year may exceed its taxable income for that year and, accordingly, a portion of such distributions may constitute a return of capital for federal income tax purposes. The specific tax characteristics of New Mountain Guardian's distributions will be reported to stockholders after the end of the calendar year. Please refer to "Material Federal Income Tax Considerations" for further information regarding the tax treatment of New Mountain Guardian's distributions and the tax consequences of New Mountain Guardian's retention of net capital gains. We can offer no assurance that NMG LLC will achieve results that will permit the payment of any cash distributions to New Mountain Guardian's stockholders and, if NMG LLC issues senior securities, NMG LLC will be prohibited from making distributions to its members, including New Mountain Guardian, if doing so causes NMG LLC to fail to maintain the asset coverage ratios stipulated by the 1940 Act or if distributions to its members are limited by the terms of any of NMG LLC's borrowings. See "Regulation", "Material Federal Income Tax Considerations" and "Senior Securities".

          New Mountain Guardian has adopted an "opt out" dividend reinvestment plan for its common stockholders. As a result, if New Mountain Guardian makes a distribution, then your cash distributions will be automatically reinvested in additional shares of New Mountain Guardian's

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common stock, unless you specifically "opt out" of the dividend reinvestment plan so as to receive cash distributions. Cash distributions reinvested in additional shares of New Mountain Guardian's common stock will be automatically reinvested by New Mountain Guardian in additional common membership units of NMG LLC, and, if New Mountain Guardian uses newly issued shares to implement the dividend reinvestment plan, it will receive, on a one-for-one basis, additional common membership units of NMG LLC in exchange for such reinvested distributions. See "Formation Transactions and Related Agreements — Structure-Related Agreements — NMG LLC Agreement" and "Dividend Reinvestment Plan". Guardian Partners intends to "opt out" of the dividend reinvestment plan. Accordingly, any cash distributions payable to Guardian Partners will not be reinvested in shares of New Mountain Guardian's common stock. In addition, Guardian AIV Holdings does not intend to reinvest any distributions received from NMG LLC in additional common membership units of NMG LLC.

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CAPITALIZATION

          The following table sets forth our capitalization as of March 31, 2010:

•

on an actual basis;



•

on an as adjusted basis to give effect to:



•

the completion of the formation transactions and the concurrent private placement;



•

the sale of             shares of New Mountain Guardian's common stock in this offering at an assumed initial public offering price of $             per share (the mid-point of the range set forth on the cover of this prospectus), after deducting estimated underwriting discounts and commissions and organizational and offering expenses payable by NMG LLC;



•

the temporary repayment of indebtedness under NMG LLC's credit facility; and



•

the assumption that all of Guardian AIV Holdings' common membership units of NMG LLC had been exchanged for the corresponding number of shares of New Mountain Guardian's common stock.