EXHIBIT 32.1

CERTIFICATION PURSUANT TO 18 U.S.C. § 1350, AS ADOPTED PURSUANT TO
SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

     Pursuant to 18 U.S.C. § 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, in connection with the Quarterly Report on Form 10-Q of Quicksilver Resources Inc. (the “Company”) for the quarter ended March 31, 2009 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), the undersigned, Philip Cook, Senior Vice President — Chief Financial Officer of the Company, and Glenn Darden, President and Chief Executive Officer of the Company, each certifies that, to his knowledge:

(1)	The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and
(2)	The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company as of the dates and for the periods expressed in the Report.

Date: May 6, 2009

By:	/s/ Philip Cook Philip Cook	By:	/s/ Glenn Darden Glenn Darden
	Senior Vice President — Chief Financial Officer		President and Chief Executive Officer