Kerfoot will lose more than $37,000 in salary and miss games Wednesday in Detroit and Friday in Buffalo. He had no prior disciplinary history with the league.
He will be eligible to return when Toronto hosts Buffalo on Saturday.
In Saturday's game in Denver, Kerfoot cross-checked Johnson from behind and sent him crashing into the boards behind the Colorado goal in the second period. Kerfoot was assessed a minor penalty for boarding.
He has five goals and three assists in 22 games this season.