Andersen missed the last eight games due to a groin injury and illness. He last played on Dec. 22 against the New York Rangers and made 25 saves in a 5-3 win.
Michael Hutchinson filled in for the returning goaltender in five games, but Garret Sparks will back up Andersen against the Avalanche in his return from a concussion. Toronto was 4-4-0 while Andersen was out.
"I'm happy to be back and looking forward to be back playing again," Andersen told reporters before the game. "I think anyone will say that it [stinks] to look from the outside in and see the guys playing without you. You want to be part of the team and part of the battle for every game."
Andersen has a 20-9-1 record with a 2.50 goals-against average and .923 save percentage in 30 games this season. He stands at third in the NHL in wins, sitting behind Vegas Golden Knights goalie Marc-Andre Fleury (26) and San Jose's Martin Jones (21).
The Maple Leafs (28-14-2) are second in the Atlantic Division with 58 points. Toronto is 2-4-0 in its last six games.
Avalanche goaltender Semyon Varlamov opposes Andersen. Colorado has lost three consecutive games and are 1-7-2 in the past 10.