The 76ers were 43-30 this season and had woefully underachieved in a year when they were expected to be serious contenders in the Eastern Conference.
Instead, they weren't close, and the move was expected after the sixth-seeded Sixers were swept by the Boston Celtics.
Brown had guided the 76ers back from the bottom of the NBA but someone else will try to take them further.
“I have a tremendous level of respect for Brett both personally and professionally and appreciate all he’s done for the 76ers organization and the City of Philadelphia,” genreal manager Elton Brand said in a statement. “He did many positive things during his time here, developing young talent and helping position our team for three straight postseason appearances. Unfortunately, we fell well short of our goals this year and I believe it is best to go in a new direction."