The 2003 Tennis Masters Cup was a men's tennis tournament played on outdoor hard courts.

It was the 34th edition of the year-end singles championships and the 29th edition of the year-end doubles championships, and was part of the 2003 ATP Tour.

It took place at the Westside Tennis Club in Houston, Texas in the United States from November 8 through November 16, 2003.

[3] Roger Federer defeated Andre Agassi 6–3, 6–0, 6–4 Bob Bryan / Mike Bryan defeated Michaël Llodra / Fabrice Santoro 6–7(6–8), 6–3, 3–6, 7–6(7–3), 6–4