<PAGE>   1
                                                                     EXHIBIT 4.2


                          AMENDMENT TO RIGHTS AGREEMENT


     AMENDMENT, dated as of September 24, 2001, between ELOYALTY CORPORATION, a
Delaware corporation (the "Company"), and MELLON INVESTOR SERVICES LLC (formerly
known as ChaseMellon Shareholder Services, L.L.C.), a New Jersey limited
liability company (the "Rights Agent"), to the Rights Agreement, dated as of
March 17, 2000, by and between the Company and the Rights Agent (the "Rights
Agreement").

     WHEREAS, the Company wishes to exercise its right to amend the Rights
Agreement pursuant to Section 27 thereof.

     Accordingly, the parties hereby agree as follows:

     1.   Definitions. Each capitalized term defined in the Rights Agreement
          shall have the same meaning in this Amendment as in the Rights
          Agreement, unless otherwise provided herein.

     2.   First Amendment. The definition of "Acquiring Person" in Section 1(a)
          is amended by inserting the following at the end thereof:

          Notwithstanding anything in this Section 1(a) to the contrary, none of
          TCV IV, L.P., TCV IV Strategic Partners, L.P., TCV III (GP), TCV III,
          L.P., TCV III (Q), L.P., TCV III Strategic Partners, L.P. or Jay Hoag,
          or their respective spouses, Associates, Affiliates, or Subsidiaries
          (collectively, the "TCV Persons"), either individually, collectively
          or in any combination, shall be deemed to be an Acquiring Person ;
          provided that all of the TCV Persons do not beneficially own, in the
          aggregate, more than 35% of the shares of Common Stock then
          outstanding. Notwithstanding anything in this Section 1(a) to the
          contrary, none of Sutter Hill Ventures, Sutter Hill Entrepreneurs Fund
          (AI), L.P., Sutter Hill Entrepreneurs Fund (QP), L.P. and Sutter Hill
          Associates, L.P. or Tench Coxe, or their respective spouses,
          Associates, Affiliates, or Subsidiaries (collectively, the "Sutter
          Hill Persons"), either individually, collectively or in any
          combination, shall be deemed to be an Acquiring Person; provided that
          all of the Sutter Hill Persons do not beneficially own, in the
          aggregate, more than 20% of the shares of Common Stock then
          outstanding.

     3.   Second Amendment. The definition of "Common Stock" in Section 1(a) is
          amended by inserting the following at the end thereof:

          Whenever used herein, the phrase "Common Stock then outstanding" shall
          be deemed to include both then outstanding shares of Common Stock and
          shares of Common Stock issuable upon conversion of then outstanding
          shares of the Series B Preferred Stock (determined without reference
          to the restriction on the conversion thereof during the six months
          following the original issuance thereof).



<PAGE>   2

     4.   Third Amendment. The definition of "Beneficial Owner" set forth in
          Section 1(d) is amended by adding the following sentence as the final
          sentence of Section 1(d):

          "Notwithstanding anything to the contrary contained herein, no TCV
          Person or Sutter Hill Person shall be deemed to be the "Beneficial
          Owner" of, or be deemed to "beneficially own," any shares of Common
          Stock solely as a result of the receipt of rights to purchase Series B
          Preferred Stock issued by the Company in connection with the
          transactions contemplated by that Share Purchase Agreement dated as of
          September 24, 2001 by and among the Company and the investors named in
          Exhibit A thereto."

     5.   Fourth Amendment. Section 1 is amended by adding the following
          immediately after subsection (n) thereof:

          "(o) "Series B Preferred Stock" means the 7% Series B Convertible
          Preferred Stock, $0.01 par value per share, of the Company."

     6.   Rights Agreement. Except as amended hereby, the Rights Agreement shall
          remain in full force and effect.

     7.   Governing Law. This Amendment shall be deemed to be a contract made
          under the laws of the State of Delaware and for all purposes shall be
          governed by and construed in accordance with the laws of Delaware
          applicable to contracts made and to be performed entirely within such
          State.

     8.   Counterparts. This Amendment may be executed in any number of
          counterparts and each such counterpart shall for all purposes be
          deemed to an original, and all such counterparts shall together
          constitute but one and the same instrument.

     9.   Descriptive Headings. Descriptive headings of the Sections of this
          Amendment are inserted for convenience only and shall not control or
          affect the meaning or construction of any of the provisions hereof.



                                       2
<PAGE>   3

     IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
duly executed and attested, all as of the day and year first above written.


eLOYALTY CORPORATION


/s/ Kelly D. Conway
-------------------
Name:  Kelly D. Conway                             ATTEST:
Title: President and Chief Executive Officer


                                                   /s/ Deidre D. Gold
                                                   ------------------
                                                   Name:   Deidre D. Gold
                                                   Title:  Vice President and
                                                           General Counsel






                                       3
<PAGE>   4

                                               MELLON INVESTOR SERVICES LLC
                                               (formerly ChaseMellon Shareholder
                                               Services, L.L.C.)

ATTEST:                                        /s/ Lee Tinto
                                               -------------
                                               Name:  Lee Tinto
                                               Title: Vice President
/s/ John J. Boryczki
--------------------
Name: John J. Boryczki
Title:   Assistant Vice President






                                       4