<PAGE>
                                                                    EXHIBIT 12.1

                                  CERTIFICATION

I, Fernando Barreira Sotelino, certify that:

1. I have reviewed this annual report on Form 20-F/A of Unibanco-Uniao de Bancos
Brasileiros S.A.;

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 company as of,
and for, the periods presented in this report;

4. The company's other certifying officers 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)) for the company 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 company, 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.       Evaluated the effectiveness of the company'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

         c.       Disclosed in this report any change in the company's internal
                  control over financial reporting that occurred during the
                  period covered by the annual report that has materially
                  affected, or is reasonably likely to materially affect, the
                  company's internal control over financial reporting; and

5. The company's other certifying officers and I have disclosed, based on our
most recent evaluation of internal control over financial reporting, to the
company's auditors and the audit committee of the company'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
                  company'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
                  company's internal control over financial reporting.

Dated: September 11, 2003



                                       By: /s/ Fernando Barreira Sotelino
                                          --------------------------------------
                                          Name: Fernando Barreira Sotelino
                                          Title: Executive President of the
                                                 Wholesale Banking Group


<PAGE>

                                  CERTIFICATION

I, Joaquim Francisco de Castro Neto, certify that:

1. I have reviewed this annual report on Form 20-F/A of Unibanco-Uniao de Bancos
Brasileiros S.A.;

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 company as of,
and for, the periods presented in this report;

4. The company's other certifying officers 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)) for the company 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 company, 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.       Evaluated the effectiveness of the company'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

         c.       Disclosed in this report any change in the company's internal
                  control over financial reporting that occurred during the
                  period covered by the annual report that has materially
                  affected, or is reasonably likely to materially affect, the
                  company's internal control over financial reporting; and

5. The company's other certifying officers and I have disclosed, based on our
most recent evaluation of internal control over financial reporting, to the
company's auditors and the audit committee of the company'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
                  company'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
                  company's internal control over financial reporting.

Dated: September 11, 2003



                                       By: /s/ Joaquim Francisco de Castro Neto
                                          --------------------------------------
                                          Name: Joaquim Francisco de Castro Neto
                                          Title: Executive President of the
                                                 Retail Banking Group

<PAGE>

                                 CERTIFICATIONS

I, Geraldo Travaglia Filho, certify that:

1. I have reviewed this annual report on Form 20-F/A of Unibanco-Uniao de Bancos
Brasileiros S.A.;

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 company as of,
and for, the periods presented in this report;

4. The company's other certifying officers 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)) for the company 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 company, 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.       Evaluated the effectiveness of the company'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

         c.       Disclosed in this report any change in the company's internal
                  control over financial reporting that occurred during the
                  period covered by the annual report that has materially
                  affected, or is reasonably likely to materially affect, the
                  company's internal control over financial reporting; and

5. The company's other certifying officers and I have disclosed, based on our
most recent evaluation of internal control over financial reporting, to the
company's auditors and the audit committee of the company'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
                  company'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
                  company's internal control over financial reporting.

Dated: September 11, 2003



                                       By: /s/ Geraldo Travaglia Filho
                                          --------------------------------------
                                          Name: Geraldo Travaglia Filho
                                          Title: Executive Officer as Chief
                                                 Financial Officer