<PAGE>


      As filed with the Securities and Exchange Commission on July 30, 2002

                          Registration No. 333- _______

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

                       SECURITIES AND EXCHANGE COMMISSION
                              WASHINGTON, DC. 20549

                                    FORM S-8

                          REGISTRATION STATEMENT UNDER
                           THE SECURITIES ACT OF 1933

                             MERCATOR SOFTWARE, INC.
             (Exact name of registrant as specified in its charter)

          Delaware                                  06-1132156
(State or other jurisdiction of                  (I.R.S. Employer
 incorporation or organization)                Identification No.)

                                 45 Danbury Road
                            Wilton, Connecticut 06897
                                 (203) 761-8600
               (Address of Principal Executive Offices) (Zip Code)

                          -----------------------------

                        1997 Employee Stock Purchase Plan
                            (Full title of the plan)

                          -----------------------------

                                   Roy C. King
    Chairman of the Board of Directors, Chief Executive Officer and President
                             Mercator Software, Inc.
                                 45 Danbury Road
                            Wilton, Connecticut 06897
                                 (203) 761-8600
           (Name and address including zip code and telephone number,
                   including area code, of agent for service)

                          -----------------------------

                                   Copies to:

                               Paul A. Soden, Esq.
                            Eileen P. McCarthy, Esq.
                                THOMPSON HINE LLP
                            One Chase Manhattan Plaza
                            New York, New York 10005
                                 (212) 344-5680

================================================================================
                         CALCULATION OF REGISTRATION FEE
<TABLE>
<CAPTION>
-----------------------------------------------------------------------------------------------------------------
<S>                     <C>               <C>                         <C>                    <C>

Title of securities     Amount to be         Proposed maximum          Proposed maximum        Amount of
  to be registered       registered       offering price per unit     aggregate offering     registration fee
                                                                             price
-----------------------------------------------------------------------------------------------------------------
Common stock, $0.01     1,415,291 (1)             $1.35 (2)              $1,910,642.85          $175.78
par value
-----------------------------------------------------------------------------------------------------------------
</TABLE>

(1) Represents additional shares reserved for issuance upon the purchase of
shares pursuant to the Registrant's 1997 Employee Stock Purchase Plan.

(2) Estimated solely for the purpose of calculating the registration fee in
accordance with Rule 457(c) and (h)(1) of Regulation C of the Securities Act of
1933, as amended, and is the average of the high and low prices of the Common
Stock as reported on The Nasdaq National Market on July 26, 2002, and is set
forth solely for purposes of calculating the filing fee for those shares without
a fixed exercise price.

Pursuant to Rule 416 under the Securities Act of 1933, there are also registered
hereunder an indeterminate amount of such additional Common Shares as may become
issuable under said Plan through the operation of applicable anti-dilution
provisions.



                                       1

<PAGE>


                                Explanatory Note

     This Registration Statement, on Form S-8, is being filed by Mercator
Software, Inc. (the "Company" or "Registrant") with the Securities and Exchange
Commission (the "SEC") pursuant to General Instruction E on Form S-8 for the
purpose of registering under the Securities Act, as amended (the "Act")
1,415,291 additional shares of Common Stock, par value $0.01 per share, of the
Company ("Common Stock") for issuance pursuant to the Company's 1997 Employee
Stock Purchase Plan.

     The Company has heretofore registered under the Act a total of 750,000
shares of Common Stock (which was subsequently split on a one for two basis,
resulting in 1,500,000 shares) for issuance under the Company's 1997 Employee
Stock Purchase Plan by means of the currently effective Registration Statement
on Form S-8 (Registration No. 333-30631) previously filed with the SEC (the
"Prior Registration Statement").

     The contents of the Prior Registration Statement are hereby incorporated by
reference into this Registration Statement.

PART II

INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 3.  Incorporation of Documents by Reference.

     The following documents of the Registrant which have been filed with the
SEC pursuant to the Securities Exchange Act of 1934, as amended (the "Exchange
Act"), are incorporated in this Registration Statement by reference as of their
respective dates:

     (a) The Registrant's Annual Report on Form 10-K for the fiscal year ended
December 31, 2001, filed with the SEC on March 18, 2002, as amended;

     (b) The Registrant's Quarterly Report on Form 10-Q for the fiscal quarter
ended March 31, 2002 filed with the SEC on May 15,2002;

     (c) "Description of Registrant's Securities to be Registered" contained in
the Registrant's registration statement on Form 8-A filed with the SEC on June
6, 1997 pursuant to Section 12(g) of the Exchange Act and incorporating by
reference the information contained in the Registrant's Registration Statement
on Form S-1 (SEC File No. 333-27293) initially filed with the SEC on March 6,
1997 as amended.

     All documents subsequently filed with the SEC by the Registrant pursuant to
Sections 13(a), 13(c), 14 and 15(d) of the Exchange Act, prior to the filing of
a post-effective amendment which indicates that all securities offered herein
have been sold or which deregisters all securities then remaining unsold, shall
be deemed to be incorporated by reference in this Registration Statement and to
be a part hereof from the date of filing of such documents.

     Any statement contained herein or in a document incorporated or deemed to
be incorporated by reference herein shall be deemed to be modified or superseded
for purposes hereof to the extent that a statement contained herein or in any
other subsequently filed document which is also incorporated or deemed to be
incorporated by reference herein 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.

                                       2

<PAGE>

Item 8.  Exhibits.

    Exhibit No.                    Description of Exhibit
    -----------                    ----------------------

       4.1        Amended and Restated Certificate of Incorporation, as amended,
                  of the Registrant (filed as Exhibit 3.1 to the Registrant's
                  Quarterly Report on Form 10-Q on November 14, 2000, File No.
                  000-22667 (7674707), and incorporated by reference herein).*

       4.2        Amended and Restated By-Laws of the Registrant (filed as
                  Exhibit 3.1 to the Registrant's Registration Statement on
                  Form 8-A on September 4, 1998, File No. 000-22667 (98704715),
                  and incorporated by reference herein).*

       4.3        1997 Employee Stock Purchase Plan, as amended, of the
                  Registrant (filed as Exhibit 10.04 to the Registrant's
                  Registration Statement on Form S-1, File No. 333-27293 and
                  incorporated by reference herein).*

       5.1        Opinion of Thompson Hine LLP.**

       23.1       Consent of Thompson Hine LLP (contained in its opinion as
                  Exhibit 5.1).

       23.2       Consent of KPMG, LLP.**

       24.1       Power of Attorney (included as part of the signature page of
                  this Registration Statement).



*Not-filed herewith. In accordance with Rule 411 promulgated pursuant to the
Securities Act of 1933, as amended, reference is made to the documents
previously filed with the SEC, which are incorporated by reference herein.
**Filed herewith.


                                      3

<PAGE>

                                   SIGNATURES


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 Wilton, the State of Connecticut, on this 30th day of
July 2002.

                                     MERCATOR SOFTWARE, INC.


                                     By: /s/ Roy C. King
                                         --------------------------------------
                                         Roy C. King
                                         Chairman of the Board of Directors,
                                         Chief Executive Officer and President


                                POWER OF ATTORNEY

     EACH SUCH PERSON WHOSE SIGNATURE appears below constitutes and appoints,
jointly and severally, Roy C. King and Kenneth J. Hall and each of them, with
full power to act without the other, his true and lawful attorney-in-fact and
agent, with the power of substitution and resubstitution, for him and in his
name, place and stead, in any and all capacities, to sign any amendments to this
Registration Statement on Form S-8 (including post-effective amendments) and to
file the same, with all exhibits thereto, and other documents in connection
therewith, with the Securities and Exchange Commission, hereby ratifying and
confirming all that said attorney-in-fact, or his or her substitute or
substitutes, may 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 by the following persons in the
capacities and on the date indicated.

Signature                         Title                            Date

PRINCIPAL EXECUTIVE OFFICER
AND DIRECTOR

/s/ Roy C. King                   Chairman of the Board of         July 30, 2002
-----------------------           Directors, Chief Executive
Roy C. King                       Officer and President

PRINCIPAL FINANCIAL AND
PRINCIPAL ACCOUNTING OFFICER

/s/  Kenneth J. Hall              Executive Vice President,        July 30, 2002
-----------------------           Chief Financial Officer and
Kenneth J. Hall                   Treasurer


Additional Directors

/s/   Constance F. Galley
-----------------------
Constance F. Galley

/s/  Ernest E. Keet
-----------------------
Ernest E. Keet

/s/ Michael E. Lehman
-----------------------
Michael E. Lehman

/s/ James P. Schadt
-----------------------
James P. Schadt


-----------------------
Dennis G. Sisco

/s/ Mark C. Stevens
-----------------------
Mark C. Stevens



                                       4

<PAGE>

                               INDEX TO EXHIBITS

     Exhibit                            Description of Exhibit
     -------                            ----------------------
       4.1          Amended and Restated Certificate of Incorporation, as
                    amended, of the Registrant (filed as Exhibit 3.1 to the
                    Registrant's Quarterly Report on Form 10-Q on November 14,
                    2000, File No. 000-22667 (7674707), and incorporated by
                    reference herein).*

       4.2          Amended and Restated By-Laws of the Registrant (filed as
                    Exhibit 3.1 to the Registrant's Registration Statement on
                    Form 8-A on September 4, 1998, File No. 000-22667
                    (98704715), and incorporated by reference herein).*

       4.3          1997 Employee Stock Purchase Plan, as amended, of the
                    Registrant (filed as Exhibit 10.04 to the Registrant's
                    Registration Statement on Form S-1, File No. 333-27293 and
                    incorporated by reference herein).*

       5.1          Opinion of Thompson Hine LLP.**

       23.1         Consent of Thompson Hine LLP (contained in its opinion as
                    Exhibit 5.1).

       23.2         Consent of KPMG LLP.**

       24.1         Power of Attorney (included as part of the signature page
                    of this Registration Statement).

 * Not filed herewith. In accordance with Rule 411 promulgated pursuant to
   the Securities Act of 1933, as amended, reference is made to the documents
   previously filed with the SEC, which are incorporated by reference herein.

** Filed herewith.


                                       5
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{"company-data": {"conformed-name": "MERCATOR SOFTWARE INC", "cik": "0001039276", "assigned-sic": "7372", "irs-number": "061132156", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-97347", "film-number": "02714898"}, "business-address": {"street1": "45 DANBURY RD", "city": "WILTON", "state": "CT", "zip": "06897", "phone": "2037617600"}, "mail-address": {"street1": "45 DANBURY", "city": "WILTON", "state": "CT", "zip": "06897"}, "former-company": {"former-conformed-name": "TSI INTERNATIONAL SOFTWARE LTD", "date-changed": "19970514"}}
As filed with the Securities and Exchange Commission on July 30, 2002

                          Registration No. 333- _______

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

                       SECURITIES AND EXCHANGE COMMISSION
                              WASHINGTON, DC. 20549

                                    FORM S-8

                          REGISTRATION STATEMENT UNDER
                           THE SECURITIES ACT OF 1933

                             MERCATOR SOFTWARE, INC.
             (Exact name of registrant as specified in its charter)

          Delaware                                  06-1132156
(State or other jurisdiction of                  (I.R.S. Employer
 incorporation or organization)                Identification No.)

                                 45 Danbury Road
                            Wilton, Connecticut 06897
                                 (203) 761-8600
               (Address of Principal Executive Offices) (Zip Code)

                          -----------------------------

                        1997 Employee Stock Purchase Plan
                            (Full title of the plan)

                          -----------------------------

                                   Roy C. King
    Chairman of the Board of Directors, Chief Executive Officer and President
                             Mercator Software, Inc.
                                 45 Danbury Road
                            Wilton, Connecticut 06897
                                 (203) 761-8600
           (Name and address including zip code and telephone number,
                   including area code, of agent for service)

                          -----------------------------

                                   Copies to:

                               Paul A. Soden, Esq.
                            Eileen P. McCarthy, Esq.
                                THOMPSON HINE LLP
                            One Chase Manhattan Plaza
                            New York, New York 10005
                                 (212) 344-5680

================================================================================
                         CALCULATION OF REGISTRATION FEE
-----------------------------------------------------------------------------------------------------------------
Title of securities     Amount to be         Proposed maximum          Proposed maximum        Amount of
  to be registered       registered       offering price per unit     aggregate offering     registration fee
                                                                             price
-----------------------------------------------------------------------------------------------------------------
Common stock, $0.01     1,415,291 (1)             $1.35 (2)              $1,910,642.85          $175.78
par value
-----------------------------------------------------------------------------------------------------------------
(1) Represents additional shares reserved for issuance upon the purchase of
shares pursuant to the Registrant's 1997 Employee Stock Purchase Plan.

(2) Estimated solely for the purpose of calculating the registration fee in
accordance with Rule 457(c) and (h)(1) of Regulation C of the Securities Act of
1933, as amended, and is the average of the high and low prices of the Common
Stock as reported on The Nasdaq National Market on July 26, 2002, and is set
forth solely for purposes of calculating the filing fee for those shares without
a fixed exercise price.

Pursuant to Rule 416 under the Securities Act of 1933, there are also registered
hereunder an indeterminate amount of such additional Common Shares as may become
issuable under said Plan through the operation of applicable anti-dilution
provisions.

                                       1
Explanatory Note

     This Registration Statement, on Form S-8, is being filed by Mercator
Software, Inc. (the "Company" or "Registrant") with the Securities and Exchange
Commission (the "SEC") pursuant to General Instruction E on Form S-8 for the
purpose of registering under the Securities Act, as amended (the "Act")
1,415,291 additional shares of Common Stock, par value $0.01 per share, of the
Company ("Common Stock") for issuance pursuant to the Company's 1997 Employee
Stock Purchase Plan.

     The Company has heretofore registered under the Act a total of 750,000
shares of Common Stock (which was subsequently split on a one for two basis,
resulting in 1,500,000 shares) for issuance under the Company's 1997 Employee
Stock Purchase Plan by means of the currently effective Registration Statement
on Form S-8 (Registration No. 333-30631) previously filed with the SEC (the
"Prior Registration Statement").

     The contents of the Prior Registration Statement are hereby incorporated by
reference into this Registration Statement.

PART II

INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 3.  Incorporation of Documents by Reference.

     The following documents of the Registrant which have been filed with the
SEC pursuant to the Securities Exchange Act of 1934, as amended (the "Exchange
Act"), are incorporated in this Registration Statement by reference as of their
respective dates:

     (a) The Registrant's Annual Report on Form 10-K for the fiscal year ended
December 31, 2001, filed with the SEC on March 18, 2002, as amended;

     (b) The Registrant's Quarterly Report on Form 10-Q for the fiscal quarter
ended March 31, 2002 filed with the SEC on May 15,2002;

     (c) "Description of Registrant's Securities to be Registered" contained in
the Registrant's registration statement on Form 8-A filed with the SEC on June
6, 1997 pursuant to Section 12(g) of the Exchange Act and incorporating by
reference the information contained in the Registrant's Registration Statement
on Form S-1 (SEC File No. 333-27293) initially filed with the SEC on March 6,
1997 as amended.

     All documents subsequently filed with the SEC by the Registrant pursuant to
Sections 13(a), 13(c), 14 and 15(d) of the Exchange Act, prior to the filing of
a post-effective amendment which indicates that all securities offered herein
have been sold or which deregisters all securities then remaining unsold, shall
be deemed to be incorporated by reference in this Registration Statement and to
be a part hereof from the date of filing of such documents.

     Any statement contained herein or in a document incorporated or deemed to
be incorporated by reference herein shall be deemed to be modified or superseded
for purposes hereof to the extent that a statement contained herein or in any
other subsequently filed document which is also incorporated or deemed to be
incorporated by reference herein 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.

                                       2
Item 8.  Exhibits.

    Exhibit No.                    Description of Exhibit
    -----------                    ----------------------

       4.1        Amended and Restated Certificate of Incorporation, as amended,
                  of the Registrant (filed as Exhibit 3.1 to the Registrant's
                  Quarterly Report on Form 10-Q on November 14, 2000, File No.
                  000-22667 (7674707), and incorporated by reference herein).*

       4.2        Amended and Restated By-Laws of the Registrant (filed as
                  Exhibit 3.1 to the Registrant's Registration Statement on
                  Form 8-A on September 4, 1998, File No. 000-22667 (98704715),
                  and incorporated by reference herein).*

       4.3        1997 Employee Stock Purchase Plan, as amended, of the
                  Registrant (filed as Exhibit 10.04 to the Registrant's
                  Registration Statement on Form S-1, File No. 333-27293 and
                  incorporated by reference herein).*

       5.1        Opinion of Thompson Hine LLP.**

       23.1       Consent of Thompson Hine LLP (contained in its opinion as
                  Exhibit 5.1).

       23.2       Consent of KPMG, LLP.**

       24.1       Power of Attorney (included as part of the signature page of
                  this Registration Statement).

*Not-filed herewith. In accordance with Rule 411 promulgated pursuant to the
Securities Act of 1933, as amended, reference is made to the documents
previously filed with the SEC, which are incorporated by reference herein.
**Filed herewith.

                                      3
SIGNATURES

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 Wilton, the State of Connecticut, on this 30th day of
July 2002.

                                     MERCATOR SOFTWARE, INC.

                                     By: /s/ Roy C. King
                                         --------------------------------------
                                         Roy C. King
                                         Chairman of the Board of Directors,
                                         Chief Executive Officer and President

                                POWER OF ATTORNEY

     EACH SUCH PERSON WHOSE SIGNATURE appears below constitutes and appoints,
jointly and severally, Roy C. King and Kenneth J. Hall and each of them, with
full power to act without the other, his true and lawful attorney-in-fact and
agent, with the power of substitution and resubstitution, for him and in his
name, place and stead, in any and all capacities, to sign any amendments to this
Registration Statement on Form S-8 (including post-effective amendments) and to
file the same, with all exhibits thereto, and other documents in connection
therewith, with the Securities and Exchange Commission, hereby ratifying and
confirming all that said attorney-in-fact, or his or her substitute or
substitutes, may 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 by the following persons in the
capacities and on the date indicated.

Signature                         Title                            Date

PRINCIPAL EXECUTIVE OFFICER
AND DIRECTOR

/s/ Roy C. King                   Chairman of the Board of         July 30, 2002
-----------------------           Directors, Chief Executive
Roy C. King                       Officer and President

PRINCIPAL FINANCIAL AND
PRINCIPAL ACCOUNTING OFFICER

/s/  Kenneth J. Hall              Executive Vice President,        July 30, 2002
-----------------------           Chief Financial Officer and
Kenneth J. Hall                   Treasurer

Additional Directors

/s/   Constance F. Galley
-----------------------
Constance F. Galley

/s/  Ernest E. Keet
-----------------------
Ernest E. Keet

/s/ Michael E. Lehman
-----------------------
Michael E. Lehman

/s/ James P. Schadt
-----------------------
James P. Schadt

-----------------------
Dennis G. Sisco

/s/ Mark C. Stevens
-----------------------
Mark C. Stevens

                                       4
INDEX TO EXHIBITS

     Exhibit                            Description of Exhibit
     -------                            ----------------------
       4.1          Amended and Restated Certificate of Incorporation, as
                    amended, of the Registrant (filed as Exhibit 3.1 to the
                    Registrant's Quarterly Report on Form 10-Q on November 14,
                    2000, File No. 000-22667 (7674707), and incorporated by
                    reference herein).*

       4.2          Amended and Restated By-Laws of the Registrant (filed as
                    Exhibit 3.1 to the Registrant's Registration Statement on
                    Form 8-A on September 4, 1998, File No. 000-22667
                    (98704715), and incorporated by reference herein).*

       4.3          1997 Employee Stock Purchase Plan, as amended, of the
                    Registrant (filed as Exhibit 10.04 to the Registrant's
                    Registration Statement on Form S-1, File No. 333-27293 and
                    incorporated by reference herein).*

       5.1          Opinion of Thompson Hine LLP.**

       23.1         Consent of Thompson Hine LLP (contained in its opinion as
                    Exhibit 5.1).

       23.2         Consent of KPMG LLP.**

       24.1         Power of Attorney (included as part of the signature page
                    of this Registration Statement).

 * Not filed herewith. In accordance with Rule 411 promulgated pursuant to
   the Securities Act of 1933, as amended, reference is made to the documents
   previously filed with the SEC, which are incorporated by reference herein.

** Filed herewith.

                                       5