Casey, 44, has been associate dean for academic affairs in the faculty of arts and sciences at Harvard since 2005. Prior to that post, Casey was assistant provost at Brown University.
He earned a bachelor's degree in philosophy and economics at University of Notre Dame and a law degree from Stanford University.
Casey replaces Robert Bottoms, who last April said he would step down after serving as president of DePauw since 1986.
Casey will assume his duties at DePauw on July 1.