<PAGE>   1
   As filed with the Securities and Exchange Commission on January 16, 2001.

                                                    Registration No. 333 -
================================================================================


                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                   ----------

                                    FORM S-8
                             REGISTRATION STATEMENT
                                      under
                           THE SECURITIES ACT OF 1933

                                   ----------

                              WILLBROS GROUP, INC.
             (Exact name of registrant as specified in its charter)

          REPUBLIC OF PANAMA                             98-0160660
    (State or other jurisdiction of                   (I.R.S. Employer
    incorporation or organization)                   Identification No.)

                             DRESDNER BANK BUILDING
                             50TH STREET, 8TH FLOOR
                                 P.O. BOX 850048
                          PANAMA 5, REPUBLIC OF PANAMA
   (Address, including zip code, of registrant's principal executive offices)

                                   ----------

                      WILLBROS GROUP, INC. 1996 STOCK PLAN
                            (Full title of the plan)

                                   ----------

                                  LARRY J. BUMP
                            CHAIRMAN OF THE BOARD AND
                             CHIEF EXECUTIVE OFFICER
                              WILLBROS GROUP, INC.
                             DRESDNER BANK BUILDING
                             50TH STREET, 8TH FLOOR
                                 P.O. BOX 850048
                          PANAMA 5, REPUBLIC OF PANAMA
                                 (50-7) 263-9282
 (Name, address, including zip code, and telephone number, including area code,
                              of agent for service)

                                   ----------

                         CALCULATION OF REGISTRATION FEE

<TABLE>
<CAPTION>
=====================================================================================================

                                                Proposed maximum  Proposed maximum
    Title of securities         Amount to be     offering price       aggregate         Amount of
      to be registered        registered(1)(2)    per share(3)    offering price(3)  registration fee
----------------------------  ----------------  ----------------  -----------------  ----------------

<S>                           <C>               <C>               <C>                <C>
Common Stock, $.05 par value  1,000,000 shares       $5.82           $5,820,000           $1,455
=====================================================================================================
</TABLE>

(1)      Pursuant to Rule 416, there are also being registered such additional
         shares of Common Stock as may become issuable pursuant to the
         anti-dilution provisions of the Plan.

(2)      Each share of Common Stock is accompanied by a preferred share purchase
         right pursuant to the registrant's Rights Agreement dated April 1,
         1999, with ChaseMellon Shareholder Services, L.L.C., as Rights Agent.

(3)      Calculated pursuant to Rule 457(h). With respect to the shares of
         Common Stock being registered for which the option price is unknown,
         the fee is calculated on the basis of the average of the high and low
         sales prices for the Common Stock on the New York Stock Exchange for
         January 9, 2001. With respect to the shares of Common Stock being
         registered for which options are outstanding, the offering price is
         determined, and the fee is calculated, on the basis of the actual
         option exercise price.

================================================================================

<PAGE>   2


                                EXPLANATORY NOTE


         This Registration Statement relates to the registration of additional
shares of Common Stock of the registrant to be issued pursuant to awards granted
under the Willbros Group, Inc. 1996 Stock Plan (the "Plan"). The additional
shares relate to the amendment to the Plan to increase the number of shares of
Common Stock available for issuance under the Plan from 1,125,000 originally
available for issuance under the Plan to 2,125,000 shares. The contents of the
registrant's Registration Statement on Form S-8, Registration No. 333-18421,
filed with the Securities and Exchange Commission on December 20, 1996 (the
"Prior Registration Statement"), are hereby incorporated by reference. The Items
below contain information required in this Registration Statement that was not
included in the Prior Registration Statement.


<PAGE>   3


                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3.       INCORPORATION OF DOCUMENTS BY REFERENCE.

              The following documents heretofore filed by the registrant with
the Securities and Exchange Commission are incorporated by reference in this
Registration Statement:

              (1) The registrant's Annual Report on Form 10-K for the fiscal
                  year ended December 31, 1999;

              (2) The registrant's Quarterly Reports on Form 10-Q for the
                  quarters ended March 31, 2000, June 30, 2000, and September
                  30, 2000;

              (3) The description of the registrant's Common Stock contained in
                  the registrant's Registration Statement on Form 8-A, dated
                  July 19, 1996, and including any amendment or report
                  heretofore or hereafter filed for the purpose of updating such
                  description of the registrant's Common Stock; and

              (4) The description of the registrant's Preferred Share Purchase
                  Rights contained in the registrant's Registration Statement on
                  Form 8-A, dated April 9, 1999, and including any amendment or
                  report heretofore or hereafter filed for the purpose of
                  updating such description of the registrant's Preferred Share
                  Purchase Rights.

              In addition, all documents subsequently filed by the registrant
pursuant to Sections 13(a), 13(c), 14 and 15(d) of the Securities Exchange Act
of 1934, as amended, prior to the filing of a post-effective amendment which
indicates that all securities offered hereby have been sold or which deregisters
all securities offered hereby then remaining unsold, shall be deemed to be
incorporated by reference in this Registration Statement and to be a part hereof
from their respective dates of filing. Any statement contained in a document
incorporated by reference shall be deemed to be modified or superseded for
purposes of this Registration Statement to the extent that a statement contained
in any other subsequently filed incorporated document modifies or supersedes
such statement. Any such statement so modified or superseded shall not be
deemed, except as so modified or superseded, to constitute a part of this
Registration Statement.

ITEM 8.       EXHIBITS.

              The following documents are filed as exhibits to this Registration
Statement:

4(a)**        Amendment Number 1 to Willbros Group, Inc. 1996 Stock Plan dated
              February 24, 1999.

5*            Opinion of Arias, Fabrega & Fabrega.

23(a)*        Consent of KPMG.

23(b)*        Consent of Arias, Fabrega & Fabrega (included in Exhibit 5).

24*           Power of Attorney (included on page II-2 of this Registration
              Statement).

----------

*     Filed herewith.

**    Incorporated by reference to the registrant's Proxy Statement for Annual
      Meeting of Stockholders dated March 31, 1999.


                                      II-1
<PAGE>   4


                                   SIGNATURES

           THE REGISTRANT. Pursuant to the requirements of the Securities Act of
1933, the registrant certifies that it has reasonable grounds to believe that it
meets all of the requirements for filing on Form S-8 and has duly caused this
Registration Statement to be signed on its behalf by the undersigned, thereunto
duly authorized, in the City of Panama City, Republic of Panama on the 16th day
of January, 2001.


                                            WILLBROS GROUP, INC.


                                            By:  /s/ Larry J. Bump
                                                --------------------------------
                                                Larry J. Bump
                                                Chairman of the Board and
                                                Chief Executive Officer


              KNOW ALL MEN BY THESE PRESENTS, that each individual whose
signature appears below constitutes and appoints Larry J. Bump, Melvin F.
Spreitzer and John N. Hove, and each of them, his true and lawful
attorneys-in-fact and agents with full power of substitution, for him and in his
name, place and stead, in any and all capacities, to sign any and all amendments
(including post-effective amendments) to this Registration Statement, and to
file the same, with all exhibits thereto, and all documents in connection
therewith, with the Securities and Exchange Commission, granting unto said
attorneys-in-fact and agents, full power and authority to do and perform each
and every act and thing requisite and necessary to be done in or about the
premises, as fully to all intents and purposes as he might or could do in
person, hereby ratifying and confirming all that said attorneys-in-fact and
agents, or his or their substitutes, may lawfully do or cause to be done by
virtue hereof.

              Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed below by the following persons in the
capacities and on the dates indicated:


<TABLE>
<CAPTION>
SIGNATURE                               TITLE                                        DATE
---------                               -----                                        ----

<S>                                     <C>                                          <C>
 /s/ Larry J. Bump                      Director, Chairman of the Board and Chief    January 16, 2001
------------------------------------    Executive Officer (Principal Executive
Larry J. Bump                           Officer and Authorized Representative in
                                        the United States)


 /s/ Michael F. Curran                  Director, Vice Chairman of the Board,        January 16, 2001
------------------------------------    President and Chief Operating Officer
Michael F. Curran


 /s/ Melvin F. Spreitzer                Director, Executive Vice President, Chief    January 16, 2001
------------------------------------    Financial Officer and Treasurer
Melvin F. Spreitzer                     (Principal Financial Officer and Principal
                                        Accounting Officer)


 /s/ Guy E. Waldvogel                   Director                                     January 16, 2001
------------------------------------
Guy E. Waldvogel


 /s/ James B. Taylor, Jr.               Director                                     January 16, 2001
------------------------------------
James B. Taylor, Jr.
</TABLE>


                                      II-2
<PAGE>   5


<TABLE>
<CAPTION>
SIGNATURE                               TITLE                                        DATE
---------                               -----                                        ----

<S>                                     <C>                                          <C>
 /s/ Peter A. Leidel                    Director                                     January 16, 2001
------------------------------------
Peter A. Leidel


 /s/ John H. Williams                   Director                                     January 16, 2001
------------------------------------
John H. Williams


 /s/ Michael J. Pink                    Director                                     January 16, 2001
------------------------------------
Michael J. Pink
</TABLE>


                                      II-3
<PAGE>   6


                                INDEX TO EXHIBITS

<TABLE>
<CAPTION>
EXHIBIT
NUMBER            DESCRIPTION
-------           -----------

<S>               <C>
 4(a)**           Amendment Number 1 to Willbros Group, Inc. 1996 Stock Plan
                  dated February 24, 1999.

 5*               Opinion of Arias, Fabrega & Fabrega.

 23(a)*           Consent of KPMG.

 23(b)*           Consent of Arias, Fabrega & Fabrega (included in Exhibit 5).

 24*              Power of Attorney (included on page II-2 of this Registration
                  Statement).
</TABLE>

----------

*      Filed herewith.

**     Incorporated by reference to the registrant's Proxy Statement for Annual
       Meeting of Stockholders dated March 31, 1999.
[{"type": "S-8", "sequence": "1", "filename": "h83319s-8.txt", "description": "WILLBROS GROUP INC", "secsgml_size_bytes": 13279}]
{"company-data": {"conformed-name": "WILLBROS GROUP INC", "cik": "0000895450", "assigned-sic": "1389", "irs-number": "980160660", "state-of-incorporation": "R1", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-53748", "film-number": "1509511"}, "business-address": {"street1": "DRESDNER BANK BUILDING", "street2": "50TH STREET 8TH FLOOR  PO BOX 850048", "city": "PANAMA 5 REPUBLIC OF", "state": "R1", "zip": "00000", "phone": "5072639282"}, "mail-address": {"street1": "C/O WILLBROS USA INC", "street2": "2431 EAST 61ST STREET SUITE 700", "city": "TULSA", "state": "OK", "zip": "74136"}}
1
   As filed with the Securities and Exchange Commission on January 16, 2001.

                                                    Registration No. 333 -
================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                   ----------

                                    FORM S-8
                             REGISTRATION STATEMENT
                                      under
                           THE SECURITIES ACT OF 1933

                                   ----------

                              WILLBROS GROUP, INC.
             (Exact name of registrant as specified in its charter)

          REPUBLIC OF PANAMA                             98-0160660
    (State or other jurisdiction of                   (I.R.S. Employer
    incorporation or organization)                   Identification No.)

                             DRESDNER BANK BUILDING
                             50TH STREET, 8TH FLOOR
                                 P.O. BOX 850048
                          PANAMA 5, REPUBLIC OF PANAMA
   (Address, including zip code, of registrant's principal executive offices)

                                   ----------

                      WILLBROS GROUP, INC. 1996 STOCK PLAN
                            (Full title of the plan)

                                   ----------

                                  LARRY J. BUMP
                            CHAIRMAN OF THE BOARD AND
                             CHIEF EXECUTIVE OFFICER
                              WILLBROS GROUP, INC.
                             DRESDNER BANK BUILDING
                             50TH STREET, 8TH FLOOR
                                 P.O. BOX 850048
                          PANAMA 5, REPUBLIC OF PANAMA
                                 (50-7) 263-9282
 (Name, address, including zip code, and telephone number, including area code,
                              of agent for service)

                                   ----------

                         CALCULATION OF REGISTRATION FEE
=====================================================================================================

                                                Proposed maximum  Proposed maximum
    Title of securities         Amount to be     offering price       aggregate         Amount of
      to be registered        registered(1)(2)    per share(3)    offering price(3)  registration fee
----------------------------  ----------------  ----------------  -----------------  ----------------
Common Stock, $.05 par value  1,000,000 shares       $5.82           $5,820,000           $1,455
=====================================================================================================
(1)      Pursuant to Rule 416, there are also being registered such additional
         shares of Common Stock as may become issuable pursuant to the
         anti-dilution provisions of the Plan.

(2)      Each share of Common Stock is accompanied by a preferred share purchase
         right pursuant to the registrant's Rights Agreement dated April 1,
         1999, with ChaseMellon Shareholder Services, L.L.C., as Rights Agent.

(3)      Calculated pursuant to Rule 457(h). With respect to the shares of
         Common Stock being registered for which the option price is unknown,
         the fee is calculated on the basis of the average of the high and low
         sales prices for the Common Stock on the New York Stock Exchange for
         January 9, 2001. With respect to the shares of Common Stock being
         registered for which options are outstanding, the offering price is
         determined, and the fee is calculated, on the basis of the actual
         option exercise price.

================================================================================
2

                                EXPLANATORY NOTE

         This Registration Statement relates to the registration of additional
shares of Common Stock of the registrant to be issued pursuant to awards granted
under the Willbros Group, Inc. 1996 Stock Plan (the "Plan"). The additional
shares relate to the amendment to the Plan to increase the number of shares of
Common Stock available for issuance under the Plan from 1,125,000 originally
available for issuance under the Plan to 2,125,000 shares. The contents of the
registrant's Registration Statement on Form S-8, Registration No. 333-18421,
filed with the Securities and Exchange Commission on December 20, 1996 (the
"Prior Registration Statement"), are hereby incorporated by reference. The Items
below contain information required in this Registration Statement that was not
included in the Prior Registration Statement.
3

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3.       INCORPORATION OF DOCUMENTS BY REFERENCE.

              The following documents heretofore filed by the registrant with
the Securities and Exchange Commission are incorporated by reference in this
Registration Statement:

              (1) The registrant's Annual Report on Form 10-K for the fiscal
                  year ended December 31, 1999;

              (2) The registrant's Quarterly Reports on Form 10-Q for the
                  quarters ended March 31, 2000, June 30, 2000, and September
                  30, 2000;

              (3) The description of the registrant's Common Stock contained in
                  the registrant's Registration Statement on Form 8-A, dated
                  July 19, 1996, and including any amendment or report
                  heretofore or hereafter filed for the purpose of updating such
                  description of the registrant's Common Stock; and

              (4) The description of the registrant's Preferred Share Purchase
                  Rights contained in the registrant's Registration Statement on
                  Form 8-A, dated April 9, 1999, and including any amendment or
                  report heretofore or hereafter filed for the purpose of
                  updating such description of the registrant's Preferred Share
                  Purchase Rights.

              In addition, all documents subsequently filed by the registrant
pursuant to Sections 13(a), 13(c), 14 and 15(d) of the Securities Exchange Act
of 1934, as amended, prior to the filing of a post-effective amendment which
indicates that all securities offered hereby have been sold or which deregisters
all securities offered hereby then remaining unsold, shall be deemed to be
incorporated by reference in this Registration Statement and to be a part hereof
from their respective dates of filing. Any statement contained in a document
incorporated by reference shall be deemed to be modified or superseded for
purposes of this Registration Statement to the extent that a statement contained
in any other subsequently filed incorporated document modifies or supersedes
such statement. Any such statement so modified or superseded shall not be
deemed, except as so modified or superseded, to constitute a part of this
Registration Statement.

ITEM 8.       EXHIBITS.

              The following documents are filed as exhibits to this Registration
Statement:

4(a)**        Amendment Number 1 to Willbros Group, Inc. 1996 Stock Plan dated
              February 24, 1999.

5*            Opinion of Arias, Fabrega & Fabrega.

23(a)*        Consent of KPMG.

23(b)*        Consent of Arias, Fabrega & Fabrega (included in Exhibit 5).

24*           Power of Attorney (included on page II-2 of this Registration
              Statement).

----------

*     Filed herewith.

**    Incorporated by reference to the registrant's Proxy Statement for Annual
      Meeting of Stockholders dated March 31, 1999.

                                      II-1
4

                                   SIGNATURES

           THE REGISTRANT. Pursuant to the requirements of the Securities Act of
1933, the registrant certifies that it has reasonable grounds to believe that it
meets all of the requirements for filing on Form S-8 and has duly caused this
Registration Statement to be signed on its behalf by the undersigned, thereunto
duly authorized, in the City of Panama City, Republic of Panama on the 16th day
of January, 2001.

                                            WILLBROS GROUP, INC.

                                            By:  /s/ Larry J. Bump
                                                --------------------------------
                                                Larry J. Bump
                                                Chairman of the Board and
                                                Chief Executive Officer

              KNOW ALL MEN BY THESE PRESENTS, that each individual whose
signature appears below constitutes and appoints Larry J. Bump, Melvin F.
Spreitzer and John N. Hove, and each of them, his true and lawful
attorneys-in-fact and agents with full power of substitution, for him and in his
name, place and stead, in any and all capacities, to sign any and all amendments
(including post-effective amendments) to this Registration Statement, and to
file the same, with all exhibits thereto, and all documents in connection
therewith, with the Securities and Exchange Commission, granting unto said
attorneys-in-fact and agents, full power and authority to do and perform each
and every act and thing requisite and necessary to be done in or about the
premises, as fully to all intents and purposes as he might or could do in
person, hereby ratifying and confirming all that said attorneys-in-fact and
agents, or his or their substitutes, may lawfully do or cause to be done by
virtue hereof.

              Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed below by the following persons in the
capacities and on the dates indicated:
SIGNATURE                               TITLE                                        DATE
---------                               -----                                        ----
/s/ Larry J. Bump                      Director, Chairman of the Board and Chief    January 16, 2001
------------------------------------    Executive Officer (Principal Executive
Larry J. Bump                           Officer and Authorized Representative in
                                        the United States)

 /s/ Michael F. Curran                  Director, Vice Chairman of the Board,        January 16, 2001
------------------------------------    President and Chief Operating Officer
Michael F. Curran

 /s/ Melvin F. Spreitzer                Director, Executive Vice President, Chief    January 16, 2001
------------------------------------    Financial Officer and Treasurer
Melvin F. Spreitzer                     (Principal Financial Officer and Principal
                                        Accounting Officer)

 /s/ Guy E. Waldvogel                   Director                                     January 16, 2001
------------------------------------
Guy E. Waldvogel

 /s/ James B. Taylor, Jr.               Director                                     January 16, 2001
------------------------------------
James B. Taylor, Jr.
II-2
5
SIGNATURE                               TITLE                                        DATE
---------                               -----                                        ----
/s/ Peter A. Leidel                    Director                                     January 16, 2001
------------------------------------
Peter A. Leidel

 /s/ John H. Williams                   Director                                     January 16, 2001
------------------------------------
John H. Williams

 /s/ Michael J. Pink                    Director                                     January 16, 2001
------------------------------------
Michael J. Pink
II-3
6

                                INDEX TO EXHIBITS
EXHIBIT
NUMBER            DESCRIPTION
-------           -----------
4(a)**           Amendment Number 1 to Willbros Group, Inc. 1996 Stock Plan
                  dated February 24, 1999.

 5*               Opinion of Arias, Fabrega & Fabrega.

 23(a)*           Consent of KPMG.

 23(b)*           Consent of Arias, Fabrega & Fabrega (included in Exhibit 5).

 24*              Power of Attorney (included on page II-2 of this Registration
                  Statement).
----------

*      Filed herewith.

**     Incorporated by reference to the registrant's Proxy Statement for Annual
       Meeting of Stockholders dated March 31, 1999.