Indianapolis Mike Green matched his career high with 24 points, and No. 12 Butler used a big second-half run to beat Cleveland State, 70-55, for its fifth Horizon League championship and first automatic berth in the NCAAs since 2001.
Butler (29-3) blew a 14-point lead in the first half but pulled away again midway through the second half and took a 60-44 lead with six minutes to go on consecutive three-pointers by Drew Streicher and reserve Zach Hahn.
J'Nathan Bullock, who led Cleveland State (21-12) with 21 points, scored the next five for the Vikings, but they never came closer than 13 points the rest of the game.
Matt Howard added 16 points and Streicher scored a season-high 11 for the Bulldogs.
Both of Butler's NCAA appearances since it last won the Horizon tournament came as at-large selections.
Cleveland State, which split a pair of close games with Butler in the regular season this year, came in as the Horizon's No. 2 seed behind the top-seeded Bulldogs.