The 32-year-old Harrington, who averaged 14.2 points and 6.1 rebounds in 64 games for the Nuggets this season, had a torn meniscus in his right knee.
He suffered the injury early last month but postponed the surgery until Denver's play-off run ended with a 4-3 series loss to the Los Angeles Lakers in the first round of the play-offs.
Harrington missed only two of his team's final 13 games and played in all of their play-off encounters, scoring 24 points in Denver's 96-87 defeat by the Lakers in Game Seven on Saturday.
