Exhibit 5

                      Letterhead of Bingham McCutchen LLP
                            Three Embarcadero Center
                         San Francisco, California 94111



                                                         Our File No. 20755-0005
September 13, 2002




UnionBanCal Corporation
400 California Street, Twelfth Floor
San Francisco, CA  94104

Attention:  Morris W. Hirsch, Esq.
            Senior Vice President and
            Deputy General Counsel

REGISTRATION STATEMENT ON FORM S-4 OF UNIONBANCAL  CORPORATION FOR VALENCIA BANK
& TRUST MERGER

Ladies and Gentlemen:


We have acted as counsel to UnionBanCal  Corporation,  a California  corporation
(the  "Company"),  in  connection  with the  Registration  Statement  under  the
Securities Act of 1933, as amended (the "Act"),  of shares (the "Shares") of the
Company's  Common Stock, no par value,  pursuant to a Registration  Statement on
Form S-4 to be filed by the Company with the Securities and Exchange  Commission
on or about the date of this opinion.

The Shares are to be issued in  exchange  for  shares of  Valencia  Bank & Trust
common stock pursuant to the Agreement and Plan of Merger, dated as of August 5,
2002, by and among the Company, Union Bank of California, N.A. and Valencia Bank
& Trust (the "Merger Agreement").

As counsel to the Company,  we have reviewed the corporate  proceedings taken by
the Company with respect to the  authorization of the issuance of the Shares. We
have also examined and relied upon  originals or copies,  certified or otherwise
authenticated  to  our  satisfaction,  of  such  corporate  records,  documents,
agreements or other  instruments  of the Company as we have deemed  necessary or
advisable  for purposes of this  opinion.  As to all matters of fact  (including
factual conclusions and characterizations and descriptions of purpose, intention
or other state of mind) we have entirely relied upon certificates of officers of
the Company,  and have assumed,  without  independent  inquiry,  the accuracy of
those certificates.

We have  assumed  the  genuineness  of all  signatures,  the  conformity  to the
originals  of all  documents  reviewed  by us as copies,  the  authenticity  and
completeness of all original  documents  reviewed by us in original or copy form
and the legal competence of each individual  executing a document.  We have also
assumed  that  the  registration  requirements  of the Act  and  all  applicable
requirements of state laws regulating the sale of securities will have been duly







satisfied.  We have also assumed  that the Company  will  receive the  specified
consideration for the Shares as set forth in the Merger Agreement.

This opinion is limited solely to the California  Corporations  Code, as applied
by  courts  located  in  California,   and  the  reported   judicial   decisions
interpreting the Code.

Subject to the  foregoing,  it is our  opinion  that the  Shares  have been duly
authorized  and, upon issuance of the Shares in accordance with the terms of the
Merger Agreement, will be validly issued, fully paid and nonassessable.

We  hereby  consent  to  the  filing  of  this  opinion  as an  exhibit  to  the
Registration  Statement and as an exhibit to any further registration  statement
to be filed pursuant to Rule 462(b) under the Securities Act with respect to the
Merger  Agreement  and the Shares,  and to the  reference to this firm under the
heading "Legal Matters" in the joint proxy statement/prospectus  included in the
Registration  Statement.  In giving our consent, we do not thereby admit that we
are in the category of persons whose consent is required  under Section 7 of the
Securities  Act or the rules and  regulations  of the  Securities  and  Exchange
Commission thereunder.

Very truly yours,

/s/Bingham McCutchen LLP
BINGHAM McCUTCHEN LLP