The 2003 Horizon League men's basketball tournament took place at the end of the 2002–03 regular season.

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.

First round games at campus sites of higher seeds Second round and semifinals hosted by the top seed.