The couple were on a train near State and Lake streets about 10:20 p.m. Saturday when the woman dropped her iPhone and one of the teens picked it up, police said.
In an alert releasing the photos, police did not say how many teenagers were involved, but photos show at least half a dozen teens. Police did not release detailed descriptions of any of the teens, but said one of them was a girl or woman and the rest were men or boys.
The attackers fled the train at the State-Lake stop. The surveillance photos show the attackers at both the platform and turnstile levels of the subway station.
The man was taken to Northwestern Memorial Hospital for treatment following the attack, but police did have any detailed information about his injuries.
Anyone with information was asked to call Area Central detectives at 312-747-8382.