Exhibit 32.1

CERTIFICATION OF THE CHIEF EXECUTIVE OFFICER

AND CHIEF FINANCIAL OFFICER

PURSUANT TO

18. U.S.C. SECTION 1350,

AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

I certify pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that the Quarterly Report of Cytokinetics, Incorporated on Form 10-Q for the quarterly period ended September 30, 2013 fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934 and that information contained in such Form 10-Q fairly presents in all material respects the financial condition and results of operations of Cytokinetics, Incorporated.

Dated: November 6, 2013

/s/ Robert I. Blum

Robert I. Blum

President and Chief Executive Officer

(Principal Executive Officer)

/s/ Sharon A. Barbari

Sharon A. Barbari

Executive Vice President, Finance and

Chief Financial Officer

(Principal Financial Officer)