| Year: | 2004 |
| Conference: | Horizon League |
| Division: | I |
| Gender: | Men's |
| Teams: | 9[1] |
| 1Stroundarena: | campus sites |
| Quarterarena: | Hinkle Fieldhouse |
| Quartercity: | Indianapolis, Indiana |
| Semiarena: | Hinkle Fieldhouse |
| Semicity: | Indianapolis, IN |
| Finalarena: | U.S. Cellular Arena |
| Finalcity: | Milwaukee, Wisconsin |
| Champions: | UIC |
| Titlecount: | 2nd |
| Coach: | Jimmy Collins |
| Coachcount: | 2nd |
| Mvp: | Armond Williams |
| Mvpteam: | UIC |
The 2004 Horizon League men's basketball tournament took place at the end of the 2003–04 regular season. The better seed hosted each first round match. Butler hosted the second round and semifinals. As the highest remaining seed, Milwaukee hosted the championship game.
All Horizon League schools played in the tournament. Teams were seeded by 2003–04 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 Butler.Championship hosted by best remaining seed