Officers were called to the basement apartment at about 2:05 a.m. local time Wednesday and found the decapitated body of an adult man inside, the Chicago Tribune reported.
The man's name and age have not been determined.
Chicago Police Department News Affairs Officer Amina Greer said an 18-year-old was arrested outside the building "without incident." Officers also recovered a knife at the scene, she said.
It was unclear how the teenager and victim were related. Charges against the teen were pending.