EXHIBIT 23(a)

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

The Board of Directors
Westamerica Bancorporation:

We consent to the incorporation by reference in the registration statements (Nos.333-105537, 333-107329, and 333-119783) on Forms S-4 and S-8 of Westamerica Bancorporation and Subsidiaries of our reports dated February 26, 2009, with respect to the consolidated balance sheets of Westamerica Bancorporation and Subsidiaries as of December 31, 2008 and 2007, and the related consolidated statements of income, changes in shareholders’ equity and comprehensive income, and cash flows for each of the years in the three-year period ended December 31, 2008, and the effectiveness of internal control over financial reporting as of December 31, 2008, which reports appear in the December 31, 2008 annual report on Form 10-K of Westamerica Bancorporation and Subsidiaries.

/s/ KPMG LLP

KPMG LLP

San Francisco, California

February 26, 2009