EXHIBIT 5.1


                    [LETTERHEAD OF MANATT PHELPS PHILLIPS]


August 7, 1997



National Mercantile Bancorp
1840 Century Park East
Los Angeles, California  90067

          RE:  AMENDMENT NO. 1 TO REGISTRATION STATEMENT ON FORM S-8

Gentlemen:

          At your request, we have examined Amendment No. 1 to the Registration
Statement on Form S-8 (the "Amended Registration Statement") to be filed by
National Mercantile Bancorp, a California corporation and a registered bank
holding company under the Bank Holding Company Act of 1956, as amended (the
"Company"), with the Securities and Exchange Commission (the "Commission") in
connection with the registration under the Securities Act of 1933, as amended
(the "Securities Act"), of 22,003 shares of the Company's common stock, no par
value (the "Common Stock"), that may be issued in the aggregate upon the
exercise of awards granted under the Company's 1994 Stock Option Plan (the
"Plan").

          In rendering this opinion, we have examined such documents and records
as we deemed relevant, including, but not limited to, the following:

          1.   The Articles of Incorporation of the Company, as amended to date;

          2.   The Bylaws of the Company, as amended to date;

          3.   The Plan;

          4.   The Form of Nonqualified Stock Option Agreement and the Form of
               Incentive Stock Option Agreement (collectively the "Agreements")
               to be used in connection with the Plan;

          5.   Records of proceedings of the Company's Board of Directors and
               shareholders pertaining to the adoption or amendment of the Plan
               and the Agreements; and

          6.   The Amended Registration Statement.

 
National Mercantile Bancorp
August 7, 1997
Page 2

          With respect to the foregoing documents, we have assumed the
genuineness of all signatures, the authenticity of all documents submitted to us
as originals and the conformity to originals of all documents submitted to us as
certified or reproduced copies. We also have obtained from the officers of the
Company certificates as to such factual matters as we consider necessary for the
purpose of this opinion, and insofar as this opinion is based on such matters of
fact, we have relied on such certificates.

          On the basis of the foregoing, subject to the assumptions, limitations
and exceptions set forth herein, we are of the opinion that the 22,003 shares of
Common Stock issuable by the Company upon the exercise of awards granted
pursuant to the Plan will be, when issued and delivered against payment therefor
in accordance with the Plan, the Agreements and the Amended Registration
Statement, duly authorized, validly issued, fully paid and non-assessable.

          For the purpose of rendering the opinions set forth herein, and with
your consent, we have assumed, without investigation that: (i) all awards
granted under the Plan to date have been, and all awards to be granted under the
Plan will be, duly and validly granted in accordance with the terms of the Plan,
(ii) the consideration for the shares of Common Stock to be issued pursuant to
the exercise of such awards will be received prior to the issuance thereof,
(iii) the shares of Common Stock to be issued pursuant to the exercise of such
awards will be issued in accordance with the terms of the Plan and the
Agreements, (iv) the Amended Registration Statement will become effective under
the Securities Act prior to the issuance of any shares of Common Stock under the
Plan and no stop order suspending the effectiveness of the Amended Registration
Statement shall have been issued and no proceedings for that purpose shall have
been instituted or be pending before the Commission, (v) a prospectus will be
updated and delivered to participants in the Plan as required by the Securities
Act and the rules and regulations promulgated by the Commission thereunder and
(vi) the grant of such awards and the issuance of shares of Common Stock upon
the exercise thereof will comply with the securities laws of each state or
jurisdiction applicable thereto (other than the Securities Act).

          This opinion is limited to the current laws of the State of California
and the Securities Act and the rules and regulations promulgated by the
Commission thereunder, to present judicial interpretations thereof and to facts
as they presently exist. In rendering this opinion, we have no obligation to
revise or supplement it should the current laws of the State of California or
the Securities Act or such rules and regulations be changed by legislative
action, judicial decision or otherwise.

          This opinion is issued to you solely for use in connection with the
Amended Registration Statement and is not to be quoted or otherwise referred to
in any financial statements of the Company or related document, nor is it to be
filed with or furnished to any government agency or other person, without the
prior written consent of the undersigned in each instance.

 
National Mercantile Bancorp
August 7, 1997
Page 3



          We hereby consent to the filing of this opinion as an exhibit to the
Amended Registration Statement.


                             Very truly yours,

                             /s/ Manatt, Phelps & Phillips, LLP