| Year: | 2003 |
| Conference: | Horizon League |
| Division: | I |
| Gender: | Men's |
| Teams: | 9[1] |
| 1Stroundarena: | campus sites |
| Quarterarena: | U.S. Cellular Arena |
| Quartercity: | Milwaukee, Wisconsin |
| Semiarena: | U.S. Cellular Arena |
| Semicity: | Milwaukee, Wisconsin |
| Finalarena: | U.S. Cellular Arena |
| Finalcity: | Milwaukee, Wisconsin |
| Champions: | Milwaukee |
| Titlecount: | 1st |
| Coach: | Bruce Pearl |
| Coachcount: | 1st |
| Mvp: | Clay Tucker |
| Mvpteam: | Milwaukee |
The 2003 Horizon League men's basketball tournament took place at the end of the 2002–03 regular season. The better seed hosted each first round match. Milwaukee hosted the second round, semifinals, and championship game.
All Horizon League schools played in the tournament. Teams were seeded by 2002–03 Horizon League season record, with a tiebreaker system to seed teams with identical conference records. The top 2 teams received a bye to the semifinals and the third seed received a bye to the quarterfinals.
First round games at campus sites of higher seeds
Second round and semifinals hosted by the top seed.Championship hosted by best remaining seed