Mackey coached at Cleveland State University from 1983 to 1990 and posted a record of 144 wins and 67 losses. His teams made one NCAA and two National Invitation Tournament appearances and averaged more than 20 wins per season. His best team was the 1985-86 unit, which won a school-record 29 games and advanced all the way to the Sweet 16—becoming the first #14 seed to advance that far. It was also the first postseason bid of any sort in the program's 57-year history. Before his first-round game against Indiana, he went up to Bobby Knight saying, "Take it easy on me, big guy." Knight exploded, knowing Cleveland State would likely give the Hoosiers all they could handle with its "run n' stun" style. He became a celebrity in northeastern Ohio, with the local press dubbing him "the King of Cleveland." Cleveland State used the money from the 1986 NCAA run to build what is now the Wolstein Center.