Majerus is on leave of absence for evaluation and treatment.
Jim Crews -- a member of Majerus' staff last season -- will serve as interim coach.
Crews said "this is a difficult time" because Majerus "is not only a colleague, but a dear friend."
"We are fortunate to have a group of outstanding young men," he said.
SLU President Lawrence Biondi, S.J., said in a statement he appreciated what Majerus "has done to return SLU men's basketball to national prominence."
The Billikens are 95-60 in five years under Majerus. Last season, they went to the NCAA Tournament for the first time since 2000.
"I know that (Majerus) would like to be here with his players and coaches this season, and all of us at SLU will keep Rick in our thoughts and prayers during this difficult time," Biondi said.