<PAGE>

                                                                    EXHIBIT 10.3

                     FIRST AMENDMENT TO EMPLOYMENT AGREEMENT
                     ---------------------------------------

     This FIRST AMENDMENT TO EMPLOYMENT AGREEMENT (the "First Amendment"), is
effective as of the 2ND day of April, 2002, by and between CellStar Ltd. (the
"Employer"), CellStar Corporation, a Delaware corporation and parent company of
Employer ("Parent"), and Robert Kaiser (the "Employee").

     WHEREAS, the parties hereto are parties to that one certain Employment
Agreement effective as of December 12, 2002 (the "Employment Agreement"); and

     WHEREAS, the parties desire to amend a provision of the Employment
Agreement as set forth herein.

     NOW, THEREFORE, in consideration of the premises and the mutual covenants
herein contained, the parties hereby agree as follows:

     1.   Section 1.3(a) of the Agreement is hereby amended and restated as
follows:

          (a) Position. During the Term, the Employee shall serve as Senior Vice
              --------
     President and Chief Financial Officer of Employer, with authority, duties
     and responsibilities consistent with such position, and shall perform such
     other services for Employer, Parent and their affiliated entities
     consistent with such position as may be reasonably assigned to him from
     time to time by the Chief Executive Officer and/or the boards of directors
     of Employer and/or Parent. It is specifically understood that, over time,
     Employee desires to assume greater responsibility for business operations,
     particularly in the Employer's North American Region. In this regard,
     Employee has agreed to serve as Senior Vice President and Chief Financial
     Officer of Employer so long as Employer agrees to consider Employee for the
     position of President of the Company's North American Region. To
     demonstrate its willingness to do so, Employer agrees to pay to Employee
     the amount of $700,000 in the event Employee has not been named as Senior
     Vice President of the Parent and President of the Employer's North American
     Region on or before September 1, 2002; provided, however, that the parties
     may extend such period for an additional ninety (90) days by mutual written
     agreement. During the Term, Employee shall, if so elected or appointed,
     also accept election or appointment, and serve, as an officer and/or
     director of Employer or any of its affiliated entities and perform the
     duties appropriate thereto, without additional compensation other than as
     set forth herein. Employee's actions hereunder shall at all times be
     subject to the direction of the Chief Executive Officer and the boards of
     directors of Employer and Parent.

     2.   The terms and provisions set forth in this First Amendment shall
modify and supersede all inconsistent terms and provisions set forth in the
Agreement and except as expressly modified and superseded by this First
Amendment, the terms and provisions of the

<PAGE>

Employment Agreement are ratified and confirms and shall continue in full force
and effect.

     3.   This First Amendment may be executed in multiple counterparts, each of
which shall be deemed to be an original and all of which, taken together, shall
constitute one and the same agreement.

     4.   This First Amendment shall be governed by and construed in accordance
with the laws of the State of Texas, without giving effect to principles of
conflict of laws.

     IN WITNESS WHEREOF, the Employer and Parent have caused this First
Amendment to be executed by their officer/general partner thereunto duly
authorized, and Employee has signed this First Amendment, as of the date first
set forth above.

                                       CELLSTAR LTD.
                                       By:  National Auto Center, Inc.
                                            General Partner


                                       By: /s/ TERRY S. PARKER
                                          ---------------------------------
                                            Terry S. Parker
                                            Chief Executive Officer


                                       CELLSTAR CORPORATION


                                       By: /s/ TERRY S. PARKER
                                          ---------------------------------
                                            Terry S. Parker
                                            Chief Executive Officer


                                       /s/ ROBERT A. KAISER
                                       ------------------------------------
                                       Robert Kaiser