Nichushkin, who also had an assist, made it 2-1 with a one-timer from below the right circle off a pass from Jack Johnson during a delayed penalty.
Mikko Rantanen and Josh Manson also scored, and Alexandar Georgiev made 10 saves for the Avalanche (23-11-2), who are 4-0-1 in their past five games. Nathan MacKinnon had two assists to extend his season-opening home point streak to 19 games.
Tomas Hertl scored, and Kaapo Kahkonen made 31 saves for the Sharks (9-25-3), who have been outscored 36-11 during their losing streak.
Rantanen gave Colorado a 1-0 lead at 6:58 of the first period with a power-play goal. He converted on a one-timer off a cross-slot pass from MacKinnon.
Hertl tied it 1-1 at 16:53 of the second with his own power-play goal, beating Georgiev glove side with a wrist shot from the top of the right circle.
After Nichushkin put the Avalanche back in front, Manson scored into an empty net at 18:53 for the 3-1 final.
