Ariba (ARBA) 10-Q 2009 Q3 Quarterly report

EXHIBIT 32.1

CERTIFICATION PURSUANT TO

18 U.S.C. SECTION 1350,

AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the Quarterly Report of Ariba, Inc. (the “Company”) on Form 10-Q for the three months ended June 30, 2009 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), Robert M. Calderoni, as Chief Executive Officer of the Company, and Ahmed Rubaie, as Chief Financial Officer of the Company, each hereby certifies, pursuant to 18 U.S.C. § 1350, as adopted pursuant to § 906 of the Sarbanes-Oxley Act of 2002, that:

(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 result of operations of the Company.

/S/    ROBERT M. CALDERONI        

Robert M. Calderoni

Chief Executive Officer

August 7, 2009

/S/    AHMED RUBAIE        

Ahmed Rubaie

Executive Vice President and

Chief Financial Officer

August 7, 2009