FS KKR Capital (FSK) 10-K 2019 FY Annual report

Exhibit 32.1

CERTIFICATION of CEO PURSUANT TO

Pursuant to

Section 906 of the Sarbanes-Oxley Act of 2002 (18 U.S.C. 1350)

In connection with the Annual Report onForm 10-K for the year ended December 31, 2019 (the “Report”) of FS KKR Capital Corp. (the “Registrant”), as filed with the Securities and Exchange Commission on the date hereof, I, Michael C. Forman, the Chief Executive Officer of the Registrant, hereby certify, to the best of my knowledge, that:

(1) The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934, as amended; and

(2) The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Registrant.

Dated: February 27, 2020

/s/ Michael C. Forman

Michael C. Forman

Chief Executive Officer