<PAGE>

                                                                   Exhibit 31.1
                                                                   ------------

                                 CERTIFICATIONS

I, Mary Lynn D. Lenz, certify that:

1.    I have reviewed this quarterly report on Form 10-Q of Slade's Ferry
      Bancorp.;

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 quarterly report;

3.    Based on my knowledge, the financial statements, and other financial
      information included in this quarterly 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
      quarterly 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 13(a)-15(e) and 15(d)-15(e)) 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 quarterly report is being prepared;

      b.    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

      c.    Disclosed in this report any change in registrant's internal
            control over financial reporting that occurred during the
            registrant's most recent fiscal quarter 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 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 the 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 data; 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 14, 2007                 /s/ Mary Lynn D. Lenz
       -----------------------         ------------------------------------
                                       Mary Lynn D. Lenz
                                       President/Chief Executive Officer

                                      39