<PAGE>
                                                                  EXHIBIT 4.1


                                   [LOGO]

   NUMBER                                                        SHARES

 MFLO
                             MOLDFLOW CORPORATION

              INCORPORATED UNDER THE LAWS OF THE STATE OF DELAWARE

THIS CERTIFICATE IS TRANSFERABLE                             CUSIP  608507 10 9
IN BOSTON, MA OR NEW YORK, NY                                   COMMON STOCK


THIS CERTIFIES that


                                                                    SEE REVERSE
                                                                    FOR CERTAIN
                                                                    DEFINITIONS



is the owner of

           FULLY PAID AND NON-ASSESSABLE SHARES OF COMMON STOCK, PAR VALUE
                                   $.01 PER SHARE, OF

----------------------------- MOLDFLOW CORPORATION ---------------------------
(herein called the "Corporation"), transferable on the books of the
Corporation in person or by duly authorized attorney upon surrender of this
Certificate properly endorsed. This Certificate and the shares represented
hereby are issued and held subject to the laws of the State of Delaware and
to the Certificate of Incorporation and the By-laws of the Corporation, as
amended from time to time.

     This Certificate is not valid until countersigned and registered by the
Transfer Agent and Registrar.

     IN WITNESS WHEREOF, the Corporation has caused this Certificate to be
executed by the facsimile signatures of its duly authorized officers and
sealed with the facsimile seal of the Corporation.

     Dated:


                                        [SEAL]

        /s/ Suzanne E. Rogers                           /s/ Marc J.L. Dulude

        CHIEF FINANCIAL OFFICER,                        CHIEF EXECUTIVE OFFICER
        TREASURER AND SECRETARY                                   AND PRESIDENT



COUNTERSIGNED AND REGISTERED:
              EQUISERVE TRUST COMPANY, N.A.
                                                                 TRANSFER AGENT
                                                                  AND REGISTRAR

BY  /s/ SIGNATURE
                                                           AUTHORIZED SIGNATURE
<PAGE>

                               MOLDFLOW CORPORATION


     The Corporation is authorized to issue more than one class or series of
stock. Upon written request the Corporation will furnish without charge to
each stockholder a copy of the powers, designations, preferences and
relative, participating, optional or other special rights of each class of
stock or series thereof and the qualifications, limitations or restrictions
of such preferences and/or rights.

     The following abbreviations, when used in the inscription on the face of
this Certificate, shall be construed as though they were written out in full
according to applicable laws or regulations:

<TABLE>
<S>                                         <C>
TEN COM  -as tenants in common              UNIF GIFT MIN ACT- _________Custodian _________
TEN ENT  -as tenants by the entireties                          (Cust)             (Minor)
JT TEN   -as joint tenants with right
          of survivorship and not as                           under Uniform Gifts to Minors
          tenants in common                                    Act__________________________
                                                                         (State)

            Additional abbreviations may also be used though not in the above list.

</TABLE>

FOR VALUE RECEIVED, ______________________ HEREBY SELL, ASSIGN AND TRANSFER UNTO

PLEASE INSERT SOCIAL SECURITY OR OTHER
   IDENTIFYING NUMBER OF ASSIGNEE
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_______________________________________________________________________________
(PLEASE PRINT OR TYPEWRITE NAME AND ADDRESS, INCLUDING ZIP CODE OF ASSIGNEE)

_______________________________________________________________________________

_______________________________________________________________________________

________________________________________________________________________ SHARES

OF THE COMMON STOCK REPRESENTED BY THE WITHIN CERTIFICATE, AND DO HEREBY
IRREVOCABLY CONSTITUTE AND APPOINT

_______________________________________________________________________ ATTORNEY

TO TRANSFER THE SAID STOCK ON THE BOOKS OF THE WITHIN NAMED COMPANY WITH FULL
POWER OF SUBSTITUTION IN THE PREMISES.

DATED ___________________



                                 _____________________________________________
                         NOTICE: THE SIGNATURE TO THIS ASSIGNMENT MUST
                                 CORRESPOND WITH THE NAME AS WRITTEN UPON THE
                                 FACE OF THE CERTIFICATE IN EVERY PARTICULAR,
                                 WITHOUT ALTERATION OR ENLARGEMENT OR ANY
                                 CHANGE WHATEVER.


        SIGNATURE(S) GUARANTEED: _____________________________________________
                                 THE SIGNATURE(S) SHOULD BE GUARANTEED BY AN
                                 ELIGIBLE GUARANTOR INSTITUTION (BANKS,
                                 STOCKBROKERS, SAVINGS AND LOAN ASSOCIATIONS
                                 AND CREDIT UNIONS WITH MEMBERSHIP IN AN
                                 APPROVED SIGNATURE GUARANTEE MEDALLION
                                 PROGRAM). PURSUANT TO S.E.C. RULE 17Ad-15.