<PAGE>
                                                                    EXHIBIT 31.1


                    CERTIFICATION PURSUANT TO RULE 13a-14(a)
                   OF THE SECURITIES AND EXCHANGE ACT OF 1934
      AS ADOPTED PURSUANT TO SECTION 302 OF THE SARBANES-OXLEY ACT OF 2002

I, Brian P. McAndrews, certify that:

1. I have reviewed this quarterly report on Form 10-Q of aQuantive, Inc.;

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 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 quarterly 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 function):

   a) All significant deficiencies or 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: November 8, 2005

                                             /s/ BRIAN P. MCANDREWS
                                             ---------------------------------
                                                 Brian P. McAndrews
                                             Chief Executive Officer and
                                                     President