EXHIBIT 32.1

CERTIFICATION OF CHIEF EXECUTIVE OFFICER

UNDER SECTION 906 OF THE SARBANES OXLEY ACT OF 2002, 18 U.S.C. 1350

The undersigned, the Chief Executive Officer of KBR, Inc. (the “Company”), hereby certifies that to his knowledge, on the date hereof:

a)the Form 10-Q of the Company for the period ended June 30, 2023, filed on the date hereof with the Securities and Exchange Commission (the “Report”) fully complies with the requirements of Section l3(a) or 15(d) of the Securities Exchange Act of 1934, as amended; and

b)the information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

/s/ Stuart J. B. Bradie

Stuart J. B. Bradie

Chief Executive Officer

Date: July 27, 2023