Mitchell had 34 points, seven rebounds and six assists. Darius Garland added 20 points and 10 assists, but the Cavaliers blew their chance at a third straight win.
Evan Mobley finished with 14 points and nine rebounds after missing five games with a strained left calf.
The Cavs raced to an 18-3 lead behind 10 points from Mitchell and led 38-23 after one quarter. But Clarkson opened the second with consecutive 3-pointers, and after a Cavs 3-pointer, the Knicks ripped off an 18-0 burst to take a 47-41 lead.
The Knicks made 12 of their first 14 shots in the second, before Mobley had Cleveland’s final four baskets as New York took a 60-58 edge into the break.
Cleveland quickly regained control in the third. Mitchell slammed down a lob pass that Garland threw from beyond halfcourt to cap a 10-3 burst to open the period, and Mitchell later hit a 3-pointer to cap an 18-4 spurt that turned a 71-all tie into an 89-75 advantage for the Cavs.