UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 13)*

Oaktree Specialty Lending Corporation

(Name of Issuer)

Common Stock, par value $0.01 per share

(Title of Class of Securities)

67401P 405

(CUSIP Number)

Todd E. Molz

Managing Director and General Counsel

Oaktree Capital Management, L.P.

333 South Grand Avenue, 28th Floor

Los Angeles, California 90071

(213) 830-6300

With a copy to:

William J. Tuttle

Kirkland & Ellis LLP

1301 Pennsylvania Avenue NW

Washington, DC 20004

(202) 389-5000

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

January 23, 2023

(Date of Event Which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.   ☐

Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See §240.13d-7(b) for other parties to whom copies are to be sent.

The information required on 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 (the “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).

This statement on Schedule 13D originally filed with the Securities and Exchange Commission on July 21, 2017 (the “Original Statement”) by Oaktree Capital Management, L.P. (“Oaktree”) and the other persons named therein, as amended and supplemented by Amendment No. 1 to Schedule 13D filed with the Securities and Exchange Commission on November 1, 2017 (“Amendment No. 1”), Amendment No. 2 to Schedule 13D filed with the Securities and Exchange Commission on May 14, 2019 (“Amendment No. 2”), Amendment No. 3 to Schedule 13D filed with the Securities and Exchange Commission on November 27, 2019 (“Amendment No. 3”), Amendment No. 4 to Schedule 13D filed with the Securities and Exchange Commission on January 30, 2020 (“Amendment No. 4”), Amendment No. 5 to Schedule 13D filed with the Securities and Exchange Commission on December 15, 2020 (“Amendment No. 5”) , Amendment No. 6 to Schedule 13D filed with the Securities and Exchange Commission on March 26, 2021 (“Amendment No. 6”), Amendment No. 7 to Schedule 13D filed with the Securities and Exchange Commission on June 2, 2021 (“Amendment No. 7”), Amendment No. 8 to Schedule 13D filed with the Securities and Exchange Commission on September 22, 2021 (“Amendment No. 8”), Amendment No. 9 to Schedule 13D filed on January 13, 2022 (“Amendment No. 9”), Amendment No. 10 to Schedule 13D filed on April 1, 2022 (“Amendment No. 10”), Amendment No. 11 to Schedule 13D filed on August 16, 2022 (“Amendment No. 11”) and Amendment No. 12 to Schedule 13D filed on January 9, 2023 (“Amendment No. 12” and, together with the Original Statement, Amendment No. 1, Amendment No. 2, Amendment No. 3, Amendment No. 4, Amendment No. 5, Amendment No. 6, Amendment No. 7, Amendment No. 8, Amendment No. 9, Amendment No. 10 and Amendment No. 11, the “Prior Statements”), is hereby amended and supplemented by this Amendment No. 13 to Schedule 13D. Capitalized terms used herein and not otherwise defined have the meanings assigned to such terms in the Prior Statements. Except as otherwise provided herein, each Item of the Prior Statements remains unchanged.

All share figures in this Amendment No. 13 have been adjusted to give effect to the 1 for 3 reverse stock split completed on January 20, 2023 and effective at the commencement of trading on January 23, 2023.

Item 2. Identity and Background

Item 2 of the Prior Statements is hereby amended and supplemented as follows:

This Schedule 13D is being filed jointly, pursuant to a fourth amended and restated joint filing agreement, by (i) Oaktree, a Delaware limited partnership and a registered investment adviser under the Investment Advisers Act of 1940, as amended, whose principal business is to provide investment advisory services to investment funds and accounts; (ii) Oaktree Capital Management GP, LLC, a Delaware limited liability company (“OCM GP LLC”), whose principal business is to serve as, and perform the functions of, the general partner of Oaktree, in its capacity as such; (iii) Atlas OCM Holdings, LLC, a Delaware limited liability company (“Atlas OCM Holdings”), whose principal business is to act as the holding company and controlling entity of each of the general partner and investment adviser of certain investment funds and separately managed accounts; (iv) Oaktree Capital Group, LLC, a Delaware limited liability company (“OCG”), whose principal business is to act as the holding company and controlling entity of the general partner of certain investment funds and separately managed accounts, in its capacity as the managing member of Holdings; (v) Oaktree Capital I, L.P., a Delaware limited partnership (“Oaktree Capital I”), whose principal business is to serve as, and perform the functions of, the general partner of Oaktree Fund GP I, L.P. and to invest in securities, in its capacity as such; (vi) OCM Holdings I, LLC, a Delaware limited liability company (“Holdings I”), whose principal business is to serve as, and perform the functions of, the general partner of Oaktree Capital I and to hold limited partnership interests in Oaktree Capital I, in its capacity as such; (vii) Oaktree Holdings, LLC, a Delaware limited liability company (“Holdings”), whose principal business is to serve as, and perform the functions of, the managing member of Holdings I, in its capacity as such; (viii) Oaktree Capital Group Holdings GP, LLC, a Delaware limited liability company (“OCGH GP”), whose principal business is to serve as, and perform the functions of, the indirect owner of the class B units of each of OCG and Atlas OCM Holdings, in its capacity as such; (ix) Brookfield Corporation, an Ontario corporation (“BN”), in its capacity as the indirect owners of the class A units of each of OCG and Atlas OCM Holdings, in its capacity as such; (x) Brookfield Asset Management ULC, an unlimited liability company formed under the laws of British Columbia (“Brookfield ULC”), in its capacity as the indirect owner of the class A units of Atlas OCM Holdings, in its capacity as such; and (xi) BAM Partners Trust, a trust formed under the laws of Ontario (“BAM Partnership” and, together with Oaktree, OCM GP LLC, Atlas OCM Holdings, OCG, Oaktree Capital I and Holdings I, Holdings, OCGH GP, BN and Brookfield ULC, the “Reporting Persons”).

The Reporting Persons have entered into a fourth amended and restated joint filing agreement, dated as of January 31, 2023, a copy of which is attached hereto as Exhibit 1.

On December 9, 2022, Brookfield Corporation (formerly Brookfield Asset Management Inc.) completed a plan of arrangement pursuant to the Business Corporations Act (Ontario) (the “Arrangement”) pursuant to which, among other things, Brookfield Corporation’s historical asset management business was transferred to Brookfield ULC. Following the Brookfield Arrangement, Brookfield ULC is deemed a beneficial owner of the shares directly or indirectly held by Atlas OCM Holdings, and accordingly, has

been added as a reporting person in this Amendment No. 13. Schedule A hereto sets forth the directors and officers of Brookfield ULC as of the date hereof. Brookfield Corporation is deemed a beneficial owner of the Oaktree Shares directly or indirectly held by OCG and Holdings, and as a result of its 75% interest in Brookfield ULC, Brookfield Corporation is also deemed a beneficial owner of the Oaktree Shares and the Tannenbaum Shares beneficially owned by Brookfield ULC. Schedule B hereto sets forth the directors and officers of Brookfield Corporation as of the date hereof.

Item 5. Interest in Securities of the Issuer

Items 5(a) – 5(c) of the Prior Statements are amended and restated in their entirety as follows:

As a result of the Voting Agreement described in Item 6 of the Original Statement and Item 3 of Amendment No. 2 among Oaktree and the Tannenbaum Stockholders, Oaktree may be deemed to be beneficially own 3,598,715 shares, or approximately 4.7%, of the issued and outstanding shares of Common Stock, which shares of Common Stock (the “Tannenbaum Shares”) are held by Leonard M. Tannenbaum, the Leonard M. Tannenbaum Foundation and the Tannenbaum Family 2012 Trust (collectively, the “Tannenbaum Stockholders”).

As a result of Oaktree Capital I purchasing 92,000 shares of Common Stock in the open market, acquiring 174,714 shares of Common Stock pursuant to the Merger Agreement and acquiring 1,404,789 shares of Common Stock pursuant the Purchase Agreement, Oaktree Capital I may be deemed to beneficially own 1,671,503 shares (collectively, the “Oaktree Shares”), or approximately 2.2%, of the issued and outstanding shares of Common Stock.

OCM GP LLC, in its capacity as the general partner of Oaktree, has the ability to direct the management of Oaktree, including the power to direct the decisions of Oaktree regarding the voting and disposition of securities beneficially owned by Oaktree. Therefore, OCM GP LLC may be deemed to have indirect beneficial ownership of the Tannenbaum Shares.

Atlas OCM Holdings, in its capacity as the sole managing member of OCM GP LLC, has the ability to direct the management of OCM GP LLC, including the power to direct the decisions of OCM GP LLC regarding the voting and disposition of securities beneficially owned by OCM GP LLC. Therefore, Atlas OCM Holdings may be deemed to have indirect beneficial ownership of the Tannenbaum Shares.

Holdings I, in its capacity as the general partner of Oaktree Capital I, has the ability to direct the management of Oaktree Capital I’s business, including the power to direct the decisions of Oaktree Capital I regarding the voting and disposition of securities held by Oaktree Capital I. Therefore, Holdings I may be deemed to have indirect beneficial ownership of the Oaktree Shares.

Holdings, in its capacity as the managing member of Holdings I, has the ability to direct the management of Holding I’s business, including the power to direct the decisions of Holdings I regarding the voting and disposition of securities beneficially owned by Holdings I. Therefore, Holdings may be deemed to have indirect beneficial ownership of the Oaktree Shares.

OCG, in its capacity as managing member of Holdings, has the ability to direct the management of Holdings’ business, including the power to direct the decisions of Holdings regarding the voting and disposition of securities beneficially owned by Holdings. Therefore, OCG may be deemed to have indirect beneficial ownership of the Oaktree Shares.

OCGH GP, in its capacity as the indirect owner of the class B units of OCG, has the ability to appoint and remove certain directors of OCG and, as such, may indirectly control the decisions of OCG regarding the voting and disposition of securities beneficially owned by OCG. In addition, OCGH GP, in its capacity as the indirect owner of the class B units of Atlas OCM Holdings, has the ability to appoint and remove certain directors of Atlas OCM Holdings and, as such, may indirectly control the decisions of Atlas OCM Holdings regarding the voting and disposition of securities beneficially owned by Atlas OCM Holdings. Therefore, OCGH GP may be deemed to have indirect beneficial ownership of the Oaktree Shares and the Tannenbaum Shares.

Brookfield Corporation, in its capacity as the indirect owner of the class A units of OCG, has the ability to appoint and remove certain directors of OCG and, as such, may indirectly control the decisions of OCG regarding the voting and disposition of securities beneficially owned by Holdings. Brookfield ULC, in its capacity as the indirect owner of the class A units of Atlas OCM Holdings, has the ability to appoint and remove certain directors of Atlas OCM Holdings and, as such, may indirectly control the decisions of Atlas OCM Holdings regarding the voting and disposition of securities beneficially owned by Atlas OCM Holdings. Therefore, Brookfield ULC may be deemed to have indirect beneficial ownership of the Tannenbaum Shares. In addition, as a result of ownership of 75% of the common shares of Brookfield ULC, Brookfield Corporation is also deemed a beneficial owner of the Oaktree Shares and the Tannenbaum Shares beneficially owned by Brookfield ULC. Brookfield Corporation is a party to a voting agreement, dated December 9, 2022, with Brookfield Asset Management Ltd. (which also owns 25% of the common shares of Brookfield ULC) (the “Manager”), pursuant to which the board of directors of Brookfield ULC is fixed at four directors and each of Brookfield Corporation and the Manager have the right to nominate one-half of such directors of Brookfield ULC and have agreed to vote their shares in favor of those four nominated directors.

BAM Class B Partners Inc., as trustee of the BAM Trust, which is the sole owner of Class B Limited Voting Shares of Brookfield Corporation, has the ability to appoint one half of the board of directors of Brookfield Corporation and, as such, may indirectly control the decisions of Brookfield Corporation regarding the voting and disposition of securities beneficially owned by Brookfield Corporation.

Neither the filing of this Schedule 13D nor any of its contents shall be deemed to constitute an admission by any of the Reporting Persons that it is the beneficial owner of any of the shares of Common Stock referred to herein for the purposes of Section 13(d) of the Act, or for any other purpose, and such beneficial ownership is expressly disclaimed.

To the actual knowledge of the Reporting Persons, none of the Covered Persons directly owns any shares of Common Stock, other than Bruce A. Karsh, who beneficially owns approximately 11,142 shares of Common Stock, and John B. Frank, who beneficially owns approximately 54,262 shares of Common Stock (of which (i) approximately 14,887 shares are held directly by Mr. Frank and (ii) approximately 39,375 shares are held by a member of Mr. Frank’s family and he may be deemed to have voting and/or investment power with respect to, but he has no pecuniary interest in, such shares); provided, however, that because of each Covered Person’s status as an investment manager, manager, general partner, director, executive officer or member of a Reporting Person, a Covered Person may be deemed to be the beneficial owner of the shares of Common Stock beneficially owned by such Reporting Person. Each of the Covered Persons disclaims beneficial ownership of the shares of Common Stock reported herein, and the filing of this Schedule 13D shall not be construed as an admission that any such Covered Person is the beneficial owner of any securities covered by this statement, other than Mr. Frank with respect to shares of Common Stock directly owned by him.

SIGNATURES

After reasonable inquiry and to the best of its knowledge and belief, the undersigned certifies that the information set forth in this statement is true, complete and correct.

Dated as of January 31, 2023

SCHEDULE A

BROOKFIELD CORPORATION

SCHEDULE B

BROOKFIELD ASSET MANAGEMENT ULC

Exhibit 1

FOURTH AMENDED AND RESTATED JOINT FILING AGREEMENT

Pursuant to Rule 13d-1(k)(1) promulgated under the Securities Exchange Act of 1934, as amended, each of the undersigned acknowledges and agrees that the foregoing statement on Schedule 13D is filed on behalf of the undersigned and that all subsequent amendments to this statement on Schedule 13D shall be filed on behalf of the undersigned without the necessity of filing additional joint acquisition statements. Each of the undersigned acknowledges that it shall be responsible for the timely filing of such amendments, and for the completeness and accuracy of the information concerning it contained therein, but shall not be responsible for the completeness and accuracy of the information concerning the others, except to the extent that it knows or has reason to believe that such information is inaccurate.

Dated as of January 31, 2023.