Riley will not return to coaching, he said at an end-of-season news conference, and reiterated his support for coach Erik Spoelstra.
Spoelstra was the target of criticism this season whenever the star-studded Heat hit a losing streak or lost a close game. Spoelstra, 40, has been the Heat's coach since 2008.
Riley won four NBA championships as head coach of the Los Angeles Lakers from 1981 to 1990, and won a fifth title with the Heat in 2006. He also took the New York Knicks to the Finals in 1994.