UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13G

Under the Securities Exchange Act of 1934

(Amendment No.     )*

(Name of issuer)

(Title of class of securities)

(CUSIP number)

(Date of event which requires filing of this statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

¨ Rule 13d-1(b)

¨ Rule 13d-1(c)

x Rule 13d-1(d)

The information required in the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

SCHEDULE 13G

SCHEDULE 13G

SCHEDULE 13G

SCHEDULE 13G

SCHEDULE 13G

SCHEDULE 13G

Item 1(a) Name of issuer: New Mountain Finance Corporation

Item 1(b) Address of issuer’s principal executive offices:

787 Seventh Avenue, 48^th Floor, New York, NY 10019

2(a) Name of person filing:

2(b) Address or principal business office or, if none, residence:

For all filing persons listed in 2(a) above: One North Wacker Drive, Suite 2200, Chicago, Illinois 60606

2(c) Citizenship:

2(d) Title of class of securities:

Common Stock

2(e) CUSIP No.:

647551100

Item 3. If this statement is filed pursuant to §§240.13d–1(b) or 240.13d–2(b) or (c), check whether the person filing is a:

NOT APPLICABLE

Item 4. Ownership

Provide the following information regarding the aggregate number and percentage of the class of securities of the issuer identified in Item 1.

Adams Street 2007 Direct Fund, L.P. (“AS 2007”) is the record owner of 97,899 shares of common stock of the Issuer (“Shares”). Adams Street 2008 Direct Fund, L.P. (“AS 2008”) is the record owner of 110,348 Shares. Adams Street 2009 Direct Fund, L.P. (“AS 2009”) is the record owner of 94,828 Shares. Adams Street Direct Co-Investment Fund, L.P. (“AS Co-Investment”) is the record owner of 303,076 Shares. Adams Street Co-Investment Fund II, L.P. (“AS Co-Investment II”) is the record owner of 606,153 Shares. The Shares owned by AS 2007, AS 2008, AS 2009, AS Co-Investment, and AS Co-Investment II may be deemed to be beneficially owned by Adams Street Partners, LLC, the managing member of each of AS 2007’s, AS 2008’s, AS 2009’s, AS Co-Investment’s, and AS Co-Investment II’s respective general partners. Thomas D. Berman, David Brett, Jeffrey T. Diehl, Elisha P. Gould, Michael S. Lynn, Robin Murray, Sachin Tulyani, Craig D. Waslin, and David S. Welsh, each of whom is a partner of Adams Street Partners, LLC (or a subsidiary thereof), may be deemed to have shared voting and investment power over the Shares. Adams Street Partners, LLC and Thomas D. Berman, David Brett, Jeffrey T. Diehl, Elisha P. Gould, Michael S. Lynn, Robin Murray, Sachin Tulyani, Craig D. Waslin, and David S. Welsh disclaim beneficial ownership of the Shares except to the extent of their pecuniary interest therein.

(ii) Shared power to vote or to direct the vote 0 (for all filing persons).

(iii) Sole power to dispose or to direct the disposition of

(iv) Shared power to dispose or to direct the disposition of 0 (for all filing persons).

Instruction. For computations regarding securities which represent a right to acquire an underlying security see §240.13d–3(d)(1).

Item 5. Ownership of 5 Percent or Less of a Class. If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than 5 percent of the class of securities, check the following [ ].

NOT APPLICABLE

Instruction. Dissolution of a group requires a response to this item.

Item 6. Ownership of More than 5 Percent on Behalf of Another Person. If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required.

See response to Item 4.

Item 7. Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person. If a parent holding company or control person has filed this schedule pursuant to Rule 13d–1(b)(1)(ii)(G), so indicate under Item 3(g) and attach an exhibit stating the identity and the Item 3 classification of the relevant subsidiary. If a parent holding company or control person has filed this schedule pursuant to Rule 13d–1(c) or Rule 13d–1(d), attach an exhibit stating the identification of the relevant subsidiary.

NOT APPLICABLE

Item 8. Identification and Classification of Members of the Group

If a group has filed this schedule pursuant to §240.13d–1(b)(1)(ii)(J), so indicate under Item 3(j) and attach an exhibit stating the identity and Item 3 classification of each member of the group. If a group has filed this schedule pursuant to Rule 13d–1(c) or Rule 13d–1(d), attach an exhibit stating the identity of each member of the group.

See response to Item 4.

Item 9. Notice of Dissolution of Group. Notice of dissolution of a group may be furnished as an exhibit stating the date of the dissolution and that all further filings with respect to transactions in the security reported on will be filed, if required, by members of the group, in their individual capacity. See Item 5.

NOT APPLICABLE

Item 10. Certifications

NOT APPLICABLE

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Date: February 14, 2012

EXHIBIT 1

AGREEMENT TO MAKE A JOINT FILING

The undersigned hereby agree that this Schedule 13G is filed by and on behalf of each of them.

Date: February 14, 2012