In the 2003 NCAA Men's Division I Basketball Tournament, the Horizon League entered two teams for the first time since 1998. Milwaukee, who earned a 12 seed in its first bid to the tournament since joining the conference, lost by one point to Notre Dame in the first round. Butler, who earned both an at-large bid and a 12 seed, made its fifth tournament appearance in seven years. The Bulldogs made it to the Sweet 16 with victories over No. 20 (5 seed) Mississippi State and No. 14 (4 seed) Louisville before falling to No. 3 (1 seed) Oklahoma in the East Regional. The Bulldogs finished the year ranked No. 21 in the final ESPN/USA Today Top 25 Poll.