Gragg is set to assume the role on July 1.
"I am thrilled and humbled to join the Northwestern University family at this pivotal moment in college athletics," Gragg said. "I look forward to joining an incredible roster of coaches and staff in Evanston on this collaborative mission to help our Wildcats achieve at the highest level as students, as athletes, and as people."
Gragg previously served as athletic director at Tulsa (2013-20) and Eastern Michigan (2006-13). The 51-year-old currently serves as the NCAA’s senior VP for inclusion, education, and community engagement.
Northwestern promoted Mike Polisky to lead the school’s athletic department on May 3 after former director Jim Phillips went on to become ACC commissioner.
However, Polisky resigned just nine days into his tenure following a student-led protest after he was one of four individuals named in a sexual harassment lawsuit filed in January.