Larsson tied the game 2-2 when he deflected McNabb's left point shot past goaltender Anton Khobudin at 18:36 of the second period.
Cody Hodgson put Buffalo ahead to stay with 5:48 remaining in regulation, converting a feed from Thomas Vanek. Larsson scored again 56 seconds later, and McNabb added an insurance goal with 2:48 to play. Ryan Miller went all the way and made 34 saves.
"I liked how we refocused, especially in the third period," Sabres coach Ron Rolston said. "That's kind of a focal point for us and whether we're down a goal or tied or up a goal, we need to be able to finish games out or find a way to win games. Tonight we did that."