The NHL salary of the contract carries an average annual value of US$675,000.
Gauthier, 23, registered one assist in nine NHL games with the Maple Leafs last season.
He had 18 points (seven goals, 11 assists) in 57 regular season games and eight points in 20 playoff games for the American Hockey League’s Toronto Marlies, helping them win the 2018 Calder Cup.
The six-foot-five, 232-pound native of Laval, Que., has recorded five points in 37 career NHL games and 49 points in 159 career American Hockey League games.
Gauthier was originally selected by the Maple Leafs in the first round (21st overall) of the 2013 NHL draft.