Page 1

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , D.C. 20549 FORM 10 - K X ANNUAL REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended March 31 , 2021 OR " TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 Commission File Number : 814-00646 APOLLO INVESTMENT CORPORATION ( Exact name of Registrant as specified in its charter ) Maryland ( State or other jurisdiction of incorporation or organization ) 9 West 57th Street 37th Floor New York , New York ( Address of principal executive offices ) 52-2439556 Title of each class Common Stock , $ 0.001 par value ( I.R.S. Employer Identification No. ) 10019 ( Zip Code ) Registrant's telephone number , including area code : ( 212 ) 515-3450 Securities registered pursuant to Section 12 ( b ) of the Act : Trading symbol ( s ) . AINV Securities registered pursuant to Section 12 ( g ) of the Act : None Name of each exchange on which registered NASDAQ Global Select Market Indicate by check mark if the Registrant is a well - known seasoned issuer , as defined in Rule 405 of the Securities Act . Yes No x Indicate by check mark if the Registrant is not required to file reports pursuant to Section 13 or Section 15 ( d ) of the Act . Yes ¨ No x Indicate by check mark whether the Registrant ( 1 ) has filed all reports required to be filed by Section 13 or 15 ( d ) of the Securities Exchange Act of 1934 during the preceding 12 months ( or for such shorter period that the Registrant was required to file such reports ) , and ( 2 ) has been subject to such filing requirements for the past 90 days . Yes x No¨ Indicate by check mark whether the Registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S - T ( § 232.405 of this chapter ) during the preceding 12 months ( or for such shorter period that the Registrant was required to submit such files ) . Yes x No ¨ Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S - K ( § 229.405 of this chapter ) is not contained herein , and will not be contained , to the best of Registrant's knowledge , in definitive proxy or information statements incorporated by reference in Part III of this Form 10 - K or any amendment to this Form 10 - K . ¨ Indicate by check mark whether the Registrant is a large accelerated filer , an accelerated filer , a non - accelerated filer , or a smaller reporting company . See the definitions of " large accelerated filer , " " accelerated filer ” and “ smaller reporting company " in Rule 12b - 2 of the Exchange Act . Large accelerated filer X Accelerated filer Non - accelerated filer Smaller reporting company Indicate by check mark whether the registrant has filed a report on and attestation to its management's assessment of the effectiveness of its internal control over financial reporting under Section 404 ( b ) of the Sarbanes - Oxley Act ( 15 U.S.C. 7262 ( b ) ) by the registered public accounting firm that prepared or issued its audit report . Yes x No Indicate by check mark whether the Registrant is a shell company ( as defined in Rule 12b - 2 of the Exchange Act ) . Yes ¨ No x The aggregate market value of the common equity held by non - affiliates of the Registrant as of September 30 , 2020 was $ 0.54 billion ( based on the closing sale price of the Registrant's Common Stock on that date as reported on the NASDAQ Global Select Market ) . For the purposes of calculating this amount only , all executive officers and Directors are " affiliates " of the Registrant . As of May 19 , 2021 , there were 65,259,176 shares of the Registrant's Common Stock outstanding . DOCUMENTS INCORPORATED BY REFERENCE Portions of the Registrant's Proxy Statement for the Annual Meeting of Stockholders to be held on August 10 , 2021 are incorporated by reference in Part III of this Form 10 - K .