Hyman put in a rebound at the side of the goal crease from Mitchell Marner's shot to give the Maple Leafs a 4-3 lead.
William Nylander and Auston Matthews each had a goal and an assist, Tyler Ennis and Andreas Johnsson scored, and Frederik Andersen made 32 saves for Toronto (37-20-4), which ended a three-game losing streak.
"The way that we won the game coming from behind, it's awesome," Hyman said. "It's a good feeling. To be able to score that goal, to get the lead after being down 3-0, is pretty cool. What a win for us to end a losing streak, coming back like we did on a Saturday night against Montreal, it's a good feeling."
WATCH: [All Canadiens vs. Maple Leafs highlights]
The victory moved the Maple Leafs within three points of the Boston Bruins for second place in the Atlantic Division.
"It's a good win for our team," Toronto coach Mike Babcock said. "When it's 3-0 and they've got to turn the music on loud because they're scared what the fans will say, it's not a good feeling. I thought we were really prepared, but it goes to show you when you're young and it's a big game, you get a little off kilter sometimes when you shouldn't. Just steady on the rudder and get it done."
Andrew Shaw and Jeff Petry each had a goal and an assist, Tomas Tatar scored, and Carey Price made 31 saves for Montreal (33-22-7), which holds the first wild card into the Stanley Cup Playoffs from the Eastern Conference.
"We've been through enough adversity as a group; we should understand how to handle it but tonight we failed," Canadiens forward Brendan Gallagher said. "We didn't do a good enough job. You get up 3-0, you should come away with a win.
"But like anything we've been through, the only choice we have to really learn from this and make sure it doesn't happen again because it's a pretty [lousy] feeling."