CERTIFICATION
                                                                    Exhibit 31.1

I, Takashi Morimura, certify that:

     1.   I have  reviewed  this  quarterly  report on Form 10-Q of  UnionBanCal
          Corporation (the "Registrant");

     2.   Based on my  knowledge,  this  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 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 we 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;

     5.   The Registrant's other certifying officer 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.

Date:  August 5, 2005

                                      By:      /S/ TAKASHI MORIMURA
                                         ---------------------------------------
                                                   Takashi Morimura
                                          PRESIDENT AND CHIEF EXECUTIVE OFFICER