Adams, who had two years left on his contract, has more than two decades of NBA experience and will hold an assistant role with Golden State.
The Celtics gave Adams permission to visit with the Warriors last week. The Warriors later offered him a multiyear deal, which he accepted.
Adams, 67, joins a contender as he approaches the twilight of his coaching career. He has never held a head-coaching position but has been an assistant for the Chicago Bulls, Oklahoma City Thunder, Milwaukee Bucks, Philadelphia 76ers and San Antonio Spurs.
The defensive-minded Adams will now coach in his home state, a few hours from his alma mater, Fresno Pacific University.
“I am very happy for Ron for him to have this opportunity to coach in his home-state,” Stevens said in a statement. “We all wish Ron nothing but the best, and appreciate all that he did during his year in Boston.”