The university said it received an allegation at the end of the 2022 football season and has hired an independent attorney to handle the investigation.
"While we do not yet know whether the allegations are true, hazing is prohibited by University policy, and we take these claims seriously," school officials said in a statement.
Northwestern said hazing is prohibited, and the health and safety of students is a top priority.
Athletic director Derrick Gragg informed players and coaches of the inquiry on Wednesday, according to a source.
Northwestern did not specify if the allegation came from a player or involved players, coaches or staff, ESPN reported. The school said its athletic department will fully cooperate with Hickey during the investigation.
"The purpose of Ms. Hickey's investigation is to find the underlying truth of the allegations -- including the scope of any potential hazing activity or harmful culture," the statement concluded.
Northwestern's season ended in late November with a 1-11 record, the team's worst since it went winless in 1989. Coach Pat Fitzgerald, a former national defensive player of the year at the school, has led the program since 2006.
Evanston police said they do not have any investigations into hazing and have not made any hazing related arrests.
"After the end of the 2022 season, Northwestern received an allegation of potential hazing in the football program. While we do not yet know whether the allegations are true, hazing is prohibited by University policy, and we take these claims seriously. The health, safety and well-being of our students is the first priority. The inquiry is in its very early stages and will be rigorously fair to everyone in this process. It will focus on gathering facts and will not jump to conclusions. Northwestern strongly supports members of our community who come forward with concerns and encourages anyone to report those concerns to the University. Immediately after receiving the hazing allegation, the University appointed an outside, independent attorney, ArentFox Schiff partner Maggie Hickey, to investigate. Ms. Hickey has a wealth of experience investigating complaints, and she has the full cooperation of the University and the athletics department. Ms. Hickey will lead her investigation independently, but the University expects that Ms. Hickey's exploration will include interviews with players, coaches and staff. The purpose of Ms. Hickey's investigation is to find the underlying truth of the allegations - including the scope of any potential hazing activity or harmful culture."