The terms of the contract was not revealed by the team, but a league source told the Boston Herald Stevens, 36, will be signed for six years.
"Brad and I share a lot of the same values," said President of basketball operations Danny Ainge in a statement released by the team. "Though he is young, I see Brad as a great leader who leads with impeccable character and a strong work ethic. His teams always play hard and execute on both ends of the court. Brad is a coach who has already enjoyed lots of success, and I look forward to working with him towards Banner 18."