Exhibit 23.3

Consent of Independent Registered Public Accounting Firm

We hereby consent to the incorporation by reference in this Post-Effective Amendment No. 1 to Registration Statement No. 333-176557 on Form S-4 of ACI Worldwide, Inc. of our report dated March 11, 2011 relating to the financial statements, financial statement schedule and the effectiveness of internal control over financial reporting, which appears in S1 Corporation’s Annual Report on Form 10-K for the year ended December 31, 2010. We also consent to the reference to us under the heading “Experts” in such Registration Statement.

/s/  PricewaterhouseCoopers LLP

Atlanta, Georgia

October 13, 2011