<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 Equity Incentive 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.
                                THOMPSON HINE LLP
                            One Chase Manhattan Plaza
                            New York, New York 10005
                                 (212) 344-5680

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

                         CALCULATION OF REGISTRATION FEE

<TABLE>
<CAPTION>
----------------------------------------------------------------------------------------------
    Title of      Amount to be    Proposed maximum        Proposed maximum     Amount of
securities to be   registered   offering price per unit  aggregate offering registration fee
  registered                                                  price
----------------------------------------------------------------------------------------------
<S>               <C>           <C>                      <C>                <C>
Common            2,500,000(1)       $1.35(2)               $3,375,000         $310.50
stock, $0.01
par value
----------------------------------------------------------------------------------------------
</TABLE>

(1) Upon the filing and effectiveness of this Registration Statement on Form
S-8, the total number of shares of Common Stock registered pursuant to the 1997
Equity Incentive Plan will be 12,200,000, plus such additional shares as may be
required pursuant to the plan in the event of a stock dividend, split-up of
shares, recapitalization or other similar change in the Common Stock.

(2) Estimated, in accordance with Rule 457(c) and (h)(1) of Regulation C of the
Securities Act, the price of $1.35 per share, 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.

<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")
2,500,000 additional shares of Common Stock, par value $0.01 per share, of the
Company ("Common Stock") for issuance pursuant to the Company's 1997 Equity
Incentive Plan.

     The Company has heretofore registered under the Act a total of 9,700,000
shares of Common Stock for issuance under the Company's 1997 Equity Incentive
Plan by means of the currently effective Registration Statements on Form S-8
(Registration No. 333-37969, 333-89951, 333-32002, 333-59240 and 333-73432)
previously filed with the SEC (the "Prior Registration Statements").

     The contents of the Prior Registration Statements 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;

     (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); and

     (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 Commission 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.

<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 Equity Incentive Plan, as amended, of the Registrant
                  (filed as Exhibit 10.1 to the Registrant's Quarterly Report on
                  Form 10-Q on November 14, 2001, File No. 000-22667 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 commission, which are incorporated by reference
herein.

     **Filed herewith.

<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.

<TABLE>
<CAPTION>
Signature                                    Title                        Date
<S>                               <C>                               <C>
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
</TABLE>

<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 Equity Incentive Plan, as amended, of the Registrant (filed
                as Exhibit 10.1 to the Registrant's Quarterly Report on Form
                10-Q on November 14, 2001, File No. 000-22667 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.
[{"type": "S-8", "sequence": "1", "filename": "ds8.txt", "description": "FORM S-8", "secsgml_size_bytes": 12820}]
{"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": "333-97349", "film-number": "02714902"}, "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 Equity Incentive 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.
                                THOMPSON HINE LLP
                            One Chase Manhattan Plaza
                            New York, New York 10005
                                 (212) 344-5680

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

                         CALCULATION OF REGISTRATION FEE
----------------------------------------------------------------------------------------------
    Title of      Amount to be    Proposed maximum        Proposed maximum     Amount of
securities to be   registered   offering price per unit  aggregate offering registration fee
  registered                                                  price
----------------------------------------------------------------------------------------------
Common            2,500,000(1)       $1.35(2)               $3,375,000         $310.50
stock, $0.01
par value
----------------------------------------------------------------------------------------------
(1) Upon the filing and effectiveness of this Registration Statement on Form
S-8, the total number of shares of Common Stock registered pursuant to the 1997
Equity Incentive Plan will be 12,200,000, plus such additional shares as may be
required pursuant to the plan in the event of a stock dividend, split-up of
shares, recapitalization or other similar change in the Common Stock.

(2) Estimated, in accordance with Rule 457(c) and (h)(1) of Regulation C of the
Securities Act, the price of $1.35 per share, 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.
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")
2,500,000 additional shares of Common Stock, par value $0.01 per share, of the
Company ("Common Stock") for issuance pursuant to the Company's 1997 Equity
Incentive Plan.

     The Company has heretofore registered under the Act a total of 9,700,000
shares of Common Stock for issuance under the Company's 1997 Equity Incentive
Plan by means of the currently effective Registration Statements on Form S-8
(Registration No. 333-37969, 333-89951, 333-32002, 333-59240 and 333-73432)
previously filed with the SEC (the "Prior Registration Statements").

     The contents of the Prior Registration Statements 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;

     (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); and

     (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 Commission 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.
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 Equity Incentive Plan, as amended, of the Registrant
                  (filed as Exhibit 10.1 to the Registrant's Quarterly Report on
                  Form 10-Q on November 14, 2001, File No. 000-22667 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 commission, which are incorporated by reference
herein.

     **Filed herewith.
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
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 Equity Incentive Plan, as amended, of the Registrant (filed
                as Exhibit 10.1 to the Registrant's Quarterly Report on Form
                10-Q on November 14, 2001, File No. 000-22667 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.