The 2013 Horizon League men's basketball tournament began on March 5, 2013, and ended with the championship game on Tuesday, March 12. First round games were played on the home court of the higher-seeded team. The second round and semifinals were hosted by the No. 1 seed Valparaiso, while the highest remaining seed hosted the championship game. All Horizon League schools participated in the tournament. Teams were seeded by their regular season record, with a tiebreaker system to seed teams with identical conference records. The top two teams received a bye to the semifinals. With the departure of Butler to the Atlantic 10, there were only three first round games.