Exhibit 31.2
   1.
    
    I have reviewed this quarterly report on Form 10-Q of Mercantile Bancorp, Inc.;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(s) 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 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; andd)
    
    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; and
 5.
    
    The registrants other certifying officer(s) 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 information;
andb)
    
    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.
  /s/ Michael P. McGrathMichael P. McGrathExecutive Vice President, Treasurer, Secretary 
and Chief Financial Officer