The incident occurred last Monday at a CTA bus stop in the 4200-block of North Kimball Avenue at about 7:15 a.m.
Police said a van with the two men inside pulled up and the passenger opened the door and exposed himself. She ignored him and they drove away.
The van is described as a white-colored cargo/work van, possibly an older model.
Anyone with information is asked to contact Area North detectives at (312) 744-8200.