Ottawa has won two straight after losing five in a row and scored the game's last four goals.
Mathot's second goal of the campaign broke the tie and Ottawa added goals by Mark Borowiecki and Kyle Turris.
Robin Lehner made 33 saves to come up with the victory. Carey Price stopped 20 shots for Montreal, which has lost its last four games.
NBC reportedly holds celebs hostage to Jimmy Fallon's show
Ray Liotta sues skin care company over use of likeness