Julien sustained fractured ribs when he slipped on ice during a team-building activity during training camp in Davos, Switzerland. Canada's medical staff determined that due to the injury, he would be unable to fly to Beijing to coach in the 2022 Games.
Colliton was fired as coach of the Chicago Blackhawks on Nov. 7, 2021, after starting the season 1-9-2. He was replaced by Derek King.
Colliton had been named one of Julien's assistants Jan. 14.
"I was ecstatic to have the opportunity to work with [Julien] and under him and support him," Colliton said. "It's been outstanding. We've had a really good start to camp here. Now it's up to us to continue the foundation he's laid."
Nolan Baumgartner, a former Vancouver Canucks assistant, and Tyler Dietrich will remain as Canada's assistants for the 2022 Games.
"The foundation that [Julien] has led and the synergy he's had with Jeremy has been obvious from the very beginning," said Canada general manager Shane Doan. "[Julien] has been incredible for us. We're so grateful for what he's obviously started here and we are very confident in Jeremy.
"In Canada, we're so blessed to have incredible depth, it seems, in everything in hockey. To have Jeremy sitting here and to step in and do what he's capable of doing, we're so fortunate."
Colliton was 87-92-26 in four seasons with the Blackhawks, including 4-5 in the Stanley Cup Playoffs. Chicago defeated the Edmonton Oilers in four games in the best-of-5 Stanley Cup Qualifiers in 2020 before losing to the Vegas Golden Knights in five games in the best-of-7 Western Conference First Round.
Colliton said that he and Canada will continue to have input from Julien.
"I don't doubt he's going to want to weigh in and he should," Colliton said. "He's got so much experience and a track record of winning and he's invested a lot in this process already, getting the team ready and he built a plan as far as how we were going to prepare the team and how the team's going to play. We're just trying to move that forward.
"We're just going to keep going and he's a part of that."
Colliton said he was confident that Canada's players and staff can pull together despite the late coaching change.
"Of course it's adversity," he said. "That's something we've talked about already. As Canadians, Canadian hockey players and Team Canada, we expect to respond to adversity in the best way we should. That's what's going to make this team great and this isn't going to be the last bump in the road, likely, that we run into."
Canada's first game of the tournament is against Germany on Feb. 10.
