President of hockey operations Lou Lamoriello announced the move Thursday at the NHL draft, two weeks after Trotz won the Stanley Cup with the Washington Capitals and three days after he resigned from that job.
Trotz reportedly agreed to a five-year deal worth double what he would have made annually on a shorter contract with the Capitals.
WATCH: Barry Trotz describes moment he was handed the Stanley Cup
Hiring Trotz fresh off his Stanley Cup victory is another statement to face-of-the-franchise centre John Tavares, who can become a free agent July 1.
Finding a permanent arena at Belmont Park and ownership hiring three-time Cup-winning Lamoriello were seen as building blocks to trying to re-sign Tavares.
In the past 40 years, Trotz is just the fifth coach not to return to a Stanley Cup-winner and the first since Scotty Bowman retired after winning with Detroit in 2002. Mike Keenan in 1994 was the last coach to leave a Cup champion in a contract dispute when he did not return to the New York Rangers.