Jack Eichel scored to extend his point streak to six games, William Karlsson had two assists and Logan Thompson made 28 saves for the Golden Knights (12-2-0), who will conclude a five-game road trip Thursday at the Buffalo Sabres.
"We're resilient for sure, we're learning how to win hockey games when we're not at our best and tonight is a good example of that," Vegas coach Bruce Cassidy said. "We had some pockets of the game where we need to be better, but we stayed in most games this year and found a way to win a lot of them to be honest with you.
"Tonight was one of those ones where someone was going to have to make a play to pick us up, and it happened to be Karlsson and Reilly."
Timothy Liljegren scored twice, and Mitchell Marner had a goal and an assist for the Maple Leafs (7-4-3), who had won three in a row. Kallgren made 16 saves.
"Obviously, [we] didn't really do what we wanted to in the first or the start of that second period, but we did a better job throughout the game," Marner said. "We gave this team too many opportunities. They're going to capitalize eventually, and Kallgren did a great job just keeping us in that game as long as he could."
Liljegren put Toronto up 3-2 at 16:56 of the second period when he took a pass from Marner and one-timed a shot from the left face-off dot.
Smith tied it 3-3 at 11:43 of the third period with a short-handed goal on a 2-on-1 with Karlsson.
"It seemed like we were getting a lot of good chances [throughout the game]," Smith said. "Maybe the volume wasn't there, but I think all night we had like five or six breakaways and were kind of just looking for holes. On the power play, we kind of caught them out when they were tired at the end of it. Karlsson was able to do a great job jumping into the play, beat his guy and fortunate to cap that one off and tie the game. [It] makes a huge difference when you can swing that on a penalty kill."
Eichel put Vegas up 2-1 at 17:55 of the first period. He stole the puck from Liljegren in the offensive zone before Chandler Stephenson collected it and found Mark Stone, who then passed across the goal crease to Eichel for a tap-in.