Aerojet Rocketdyne (AJRD) 10-Q 2017 Q2 Quarterly report

Exhibit 32.1

CERTIFICATIONS

PURSUANT TO 18 UNITED STATES CODE §1350

AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

The undersigned hereby certifies that to her knowledge the quarterly report on Form 10-Q of Aerojet Rocketdyne Holdings, Inc. for the period ended June 30, 2017 (the Report), as filed with the Securities and Exchange Commission on the date hereof, fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934 and that the information contained in the Report fairly presents, in all material respects, the financial condition and results of the operations of the Company, as of the dates and the periods expressed in the Report.

/s/ Eileen P. Drake

Eileen P. Drake

Chief Executive Officer and President

(Principal Executive Officer)

Date: August 3, 2017

The undersigned hereby certifies that to his knowledge the quarterly report on Form 10-Q of Aerojet Rocketdyne Holdings, Inc. for the period ended June 30, 2017 (the Report), as filed with the Securities and Exchange Commission on the date hereof, fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934 and that the information contained in the Report fairly presents, in all material respects, the financial condition and results of the operations of the Company, as of the dates and the periods expressed in the Report.

/s/ Paul R. Lundstrom

Paul R. Lundstrom

Vice President and Chief Financial Officer

(Principal Financial Officer and Principal Accounting Officer)

Date: August 3, 2017