The Knicks battled back from and eight-point deficit in the final two minutes, forging a 108-108 tie.
Nowitzki, however, salvaged the victory for Dallas when his jumper off the glass went through for the decisive score.
Nowitzki finished with 15 points as the Mavs notched a third straight win.
Carmelo Anthony pumped in 44 points and grabbed nine rebounds for New York, losers of three straight.
Celebrity Couples of 2014 [PHOTOS]