EXHIBIT 23.1

Consent of Independent Registered Public Accounting Firm

We have issued our reports dated February 25, 2010, with respect to the consolidated financial statements (which report expressed an unqualified opinion and contained an explanatory paragraph relating to the change in accounting method for term license agreements) and internal control over financial reporting included in the Annual Report of Acacia Research Corporation on Form 10-K for the year ended December 31, 2009. We consent to the incorporation by reference of said reports in the Registration Statement of Acacia Research Corporation on Form S-8 related to the 2002 Acacia Technologies Stock Incentive Plan to be filed on or about February 26, 2010.

/s/ Grant Thornton LLP

Irvine, California

February 26, 2010