After assisting Roberto Martinez with Belgium, former Arsenal and Barcelona star Henry took up his first head coach role at Ligue 1 club Monaco in October 2018.
However, despite signing a three-year deal, Henry was dismissed in January, with his predecessor Leonardo Jardim coming in as his replacement.
Montreal, meanwhile, finished ninth in the Eastern Conference in 2019, with Wilmer Cabrera - who only took charge in August - not offered the chance to stay on as coach.
On his official unveiling as the Impact's new coach, Henry insisted he has put his poor spell at Monaco behind him and is hoping to prove his quality as a coach with Montreal, who will play in the 2020 CONCACAF Champions League.
"You have to start somewhere, that's how you acquire experience," Henry, who has signed a two-year deal with Montreal, told a news conference on Monday.
"For me it came with Belgium and Monaco, where I learned a lot about myself. It's about fighting. This isn't my story but the story of everyone in life. Everyone falls. It's about how you get up.
"It didn't work out at Monaco. I can give you a lot of excuses but at the end of the day it didn't work out and I am here as coach of Montreal.
"I learned a lot there. The only mistake you can make is not learning from what happened. You have to confront it."