| Champ: |  Andre Agassi |
| Runner: |  Davide Sanguinetti |
| Score: | 6–3, 6–1 |
| Draw: | 32 (4 / 3) |
| Seeds: | 8 |
| Type: | singles doubles |
| Main Name: | Pacific Coast Championships |
The 2003 Siebel Open was a men's international tennis tournament.Lleyton Hewitt was the defending champion but did not compete that year.
Andre Agassi won in the final 6–3, 6–1 against Davide Sanguinetti.
A champion seed is indicated in bold text while text in italics indicates the round in which that seed was eliminated.
Andre Agassi (champion)
Paradorn Srichaphan (first round) James Blake (semifinals) Jan-Michael Gambill (second round) Todd Martin (second round) Davide Sanguinetti (final)
Nikolay Davydenko (quarterfinals)