Exhibit 32.1

Certification of Principal Executive Officer

Pursuant to

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

In connection with the Quarterly Report on Form 10-Q for the quarter ended June 30, 2021 (the “Report”) of ICF International, Inc. (the “Registrant”), as filed with the Securities and Exchange Commission on the date hereof, I, John Wasson, President and Chief Executive Officer of the Registrant, hereby certify 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.

August 4, 2021	/s/ John Wasson
	John Wasson
	President and Chief Executive Officer
	(Principal Executive Officer)