UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the Securities
Exchange Act of 1934

(Amendment No. )

Filed by the Registrant ý

Filed by a Party other than the Registrant ¨

Check the appropriate box:

¨ Preliminary Proxy Statement
¨ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2))

¨ Definitive Proxy Statement
ý Definitive Additional Materials

¨ Soliciting Material Pursuant to Rule 14a-11(c) or Rule 14a-12

Apollo Investment Corporation(Name of Registrant as Specified in Its Charter)

(Name of Person(s) Filing Proxy Statement if other than the Registrant)

Payment of Filing Fee (Check the appropriate box):

ý No fee required.
    ¨ Fee computed on table below per Exchange Act Rules 14a-6(i)(l) and 0-11.

(1) Title of each class of securities to which transaction applies:

(2) Aggregate number of securities to which transaction applies:

(3) Per unit price or other underlying value of transaction computed pursuant to Exchange Act Rule 0-11 (Set forth the amount on which the filing fee is calculated and state how it was determined):

(4) Proposed maximum aggregate value of transaction:

(5) Total fee paid:

¨ Fee paid previously with preliminary materials.

¨ Check box if any part of the fee is offset as provided by Exchange Act Rule 0-11(a)(2) and identify the filing for which the offsetting fee was paid previously. Identify the previous filing by registration statement number, or the form or schedule and the date of its filing.

(1) Amount previously paid:

(2) Form, schedule or registration statement no.:

(3) Filing party:

(4) Date filed:

9 West 57th Street

New York, New York 10019

July 30, 2019

Dear Fellow Stockholder:

We are writing to remind you that the 2019 Annual Meeting of Stockholders (the “Annual Meeting”) of Apollo Investment Corporation (the “Company”) will be held in person and electronically via live webcast simultaneously on August 6, 2019 at 9:30 a.m., Eastern Daylight Time, at the New York offices of Skadden, Arps, Slate, Meagher & Flom LLP, Four Times Square, New York, New York 10036. The live webcast, which will also offer an audio stream, will be accessible over the Internet at www.virtualshareholdermeeting.com/AINV2019.

Our records indicate that as of June 12, 2019, the “Record Date” for the Annual Meeting, you held shares of the Company and, therefore, you are entitled to vote on the matters described in the Company’s Definitive Proxy Statement for the Annual Meeting (the “Proxy Statement”) and as set forth on the proxy card attached thereto, which were mailed to you on or about June 26, 2019. Our records indicate that we have not yet received your vote.

REMEMBER: Your vote is important, no matter how large or small your holdings may be. Please take a moment to vote your shares.

In particular, the Company’s Board of Directors recommends that you vote your shares in favor of the proposals described in the Proxy Statement and as set forth on the proxy card. Voting promptly may help reduce solicitation costs and will eliminate your receiving follow-up phone calls and/or mailings.

As the date of the Annual Meeting approaches, if we have not received your proxy, you may receive a phone call from a representative of Georgeson LLC (“Georgeson”), the Company’s proxy solicitor, reminding you to exercise your right to vote. Should you have any questions with regards to voting your shares, please call our proxy solicitor, Georgeson, at 1-866-277-0928.

Thank you in advance for your participation and your consideration in this extremely important matter.

Sincerely yours,

John J. Hannan

Chairman of the Board of Directors