Police said the girl was seen performing a sexual act on a male in the 200-block of 89th Place at about 1:30 p.m. Thursday through an online remote learning application.
Police responded and took a man into custody. The girl was taken to Comer Children's Hospital for evaluation. Her condition has not been released.
An investigation by Area Two detectives into the incident is ongoing.
Police did not say who witnessed the incident or whether the online learning application was associated with a specific school.
The Sun-Times Media Wire contributed to this report.