Stanley Pringle added 17 points for Penn State, which outscored Northwestern 45-33 in the second half.
The loss spoiled the return of Kevin Coble, who missed the first nine games to be with his mom, Carlys, in Phoenix while she underwent treatment for cancer. Coble, a Big Ten All-Freshman selection last year after leading the Wildcats in scoring and rebounding, finished with 11 points.
Michael Thompson led Northwestern with 17 points and 10 assists, while Jason Okrzesik added 14 points.
After being held scoreless in the first half, Talor Battle sparked a 20-4 Penn State run to open the second half and turn the game into a rout.
Battle scored eight during the spurt, including a pair of 3-pointers, and Claxton hit a pair of free throws with 12:34 left to cap the stretch and give the Nittany Lions a 54-39 lead.
Northwestern led by as many as nine in the first half, but Penn State went on a 14-4 run midway through to keep it close. Claxton's jumper gave the Nittany Lions their first lead, 23-22 with 5:21 left.
