The 2009 Horizon League men's basketball tournament was held at the end of the 2008–2009 regular season. The better seed hosted each first round match. The second and third rounds were played at Hinkle Fieldhouse in Indianapolis. The championship game was played at the home court of the highest remaining seed, also Hinkle Fieldhouse, the home court of the Butler men's basketball team.
Regular season standings
Cleveland State was seeded ahead of Wright State based on a better Ratings Percentage Index (RPI) score, all other tiebreakers having failed to distinguish the two teams.
Youngstown State finished ahead of Illinois-Chicago based on head-to-head record.
Bracket
First round games at campus sites of lower-numbered seeds
Second round and semifinals hosted by Butler. Championship hosted by lower-numbered remaining seed