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Exhibit 31.2

CERTIFICATION UNDER
SECTION 302 OF
THE SARBANES OXLEY ACT OF 2002


I, Jennifer J. Finger, Chief Financial Officer of the registrant, certify that:

1. I have reviewed this quarterly report for the period ending March
31, 2005 on Form 10-Q of Westamerica Bancorporation;

2. Based on my knowledge, this quarterly report does not contain any
untrue statement of a material fact or omit to state a material fact
necessary to make the statements made, in light of the circumstances
under which such statements were made, not misleading with respect
to the period covered by this report;

3. Based on my knowledge, the financial statements, and other
financial information included in this report, fairly present in all
material respects the financial condition, results of operations and
cash flows of the registrant as of, and for, the periods presented
in this report;

4. The registrant's other certifying officer(s) and I are
responsible for establishing and maintaining disclosure controls and
procedures (as defined in Exchange Act Rules 13a-15(e) and
15d-15(e)) and internal control over financial reporting (as defined
in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant
and have:

    (a) Designed such disclosure controls and procedures, or caused such
    disclosure controls and procedures to be designed under our supervision, to
    ensure that material information relating to the registrant, including its
    consolidated subsidiaries, is made known to us by others within those
    entities, particularly during the period in which this report is being
    prepared;

    (b) Designed such internal control over financial reporting, or caused such
    internal control over financial reporting to be designed under our
    supervision, to provide reasonable assurance regarding the reliability of
    financial reporting and the preparation of financial statements for external
    purposes in accordance with generally accepted accounting principles;

    (c) Evaluated the effectiveness of the registrant's disclosure controls and
    procedures and presented in this report our conclusions about the
    effectiveness of the disclosure controls and procedures, as of the end of
    the period covered by this report based on such evaluation; and

    (d) Disclosed in this report any change in the registrant's internal control
    over financial reporting that occurred during the registrant's most recent
    fiscal quarter (the registrant's fourth fiscal quarter in the case of an
    annual report) that has materially affected, or is reasonably likely to
    materially affect, the registrant's internal control over financial
    reporting; and

5. The registrant's other certifying officer(s) and I have
disclosed, based on our most recent evaluation of internal control
over financial reporting, to the registrant's auditors and the audit
committee of registrant's board of directors (or persons performing
the equivalent functions):

    (a) All significant deficiencies and material weaknesses in the design or
    operation of internal control over financial reporting which are reasonably
    likely to adversely affect the registrant's ability to record, process,
    summarize and report financial information; and

    (b) Any fraud, whether or not material, that involves management or other
    employees who have a significant role in the registrant's internal control
    over financial reporting.


/s/  Jennifer J. Finger                                          May 10, 2005
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Jennifer J. Finger                                               Date
Senior Vice President and Chief Financial Officer