EXHIBIT 31.2
 CERTIFICATION OF CHIEF FINANCIAL OFFICER OF THE REGISTRANT, 
PURSUANT TO 17 CFR 240.13a  14(a) OR
17 CFR 240.15d  14(a)
  1.
    
    I have reviewed this annual report on Form 10-K of Dynamex Inc.;2.
    
    Based on my knowledge, this annual report does not contain any untrue statements 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 annual report;3.
    
    Based on my knowledge, the financial statements, and other financial information
included in this annual report, fairly present in all material respects the financial
condition, results of operations and cash flows of Dynamex Inc. as of, and for, the
periods presented in this annual 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-14
and 15d-14) 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 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 annual 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 annual 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 annual 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
this 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;
 a.
    
    All significant deficiencies and material weaknesses in the design or
operation of internal controls which could 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 controls over
financial reporting.
 Date: September 22, 2010/s/ Ray E. SchmitzName:
    Ray E. SchmitzTitle:
    Executive Vice President and Chief Financial Officer