No contract terms were released.
Collins replaces Bill Cardody who did not get the team to the NCAA tournament in his 13 seasons at the school. He was let go after the team went 13-19 this season, but he did get the team to four straight NIT appearances from 2009 to 2012.
Collins, who spent 13 seasons at Duke, will continue to assist the Blue Devils until they are done playing in the postseason. Duke, a No. 2 seed in the Midwest region of the NCAA tournament, plays third-seeded Michigan State on Friday in the Sweet 16.
From the Northwestern release:
"I'm so grateful to President Schapiro, Chairman Osborn and Dr. Phillips for the opportunity to lead the men's basketball program at one of the premier universities in the world, to compete in the Big Ten Conference, and to do so in my hometown," said Collins. "Northwestern University is a special place that strives for excellence in every regard, and our program will be no different. I can't possibly thank Coach Krzyzewski and Duke University enough for preparing me for this day."