The four-time Super League Grand Final winner has been out of work since Leeds’ shock decision to sack him in July. He will take over from Paul Rowley who left Wolfpack, by “mutual” agreement, on Saturday.
Wakefield-born McDermott, 48, was assistant-coach at Rhinos in 2004-5 and returned to the club ahead of the 2011 season after a spell in charge of Harlequins.
A former Bradford Bulls and Great Britain forward, he is Leeds’ most successful team boss having also won the Challenge Cup and league leaders’ shield twice each and the World Club Challenge.
His immediate aim will be to steer Toronto out of the Betfred Championship into Super League. He said: “After being at the Rhinos for so long I always knew I couldn’t just roll into any other club so easily.
“Toronto Wolfpack offers a challenge and ambition that not many other clubs have, already demonstrating this with how they’ve gone about getting to this stage.
“I’m excited on being a part of something that could genuinely be a game changer for rugby league in the UK.”
Brian Noble, Toronto’s director of rugby, said: “We are delighted to bring in a head coach of Brian’s calibre, who we believe can lead us to the Super League. Brian is a world-class coach and we are extremely excited that he has come on board with the Wolfpack.
“His track record in the game speaks for itself and having known Brian for many years, I know he has all the right attributes to take the club forward.”
Toronto won League One in their debut season and topped the 2018 Championship table, but were beaten by London Broncos in the promotion-deciding million pound game. They announced six high-profile signings last month, with ex-NRL star Ricky Leutele joining the Canadian outfit alongside former Castleford Tigers prop Gadwin Springer and fellow Super League exiles Jon Wilkin, Bodene Thompson, Joe Mellor and Tom Olbison.
Their Championship rivals next year will include Featherstone Rovers, Batley Bulldogs and Dewsbury Rams.