The 15-year-old, who has not been identified because he is a juvenile, allegedly stole property from a 24-year-old woman who was riding a train near the Kostner Pink Line station, police said.
A day later, he robbed another 24-year-old woman who was riding a train near the 18th Street station, police said.
The boy was arrested by CPD's Mass Transit unit on Tuesday in the 4200 block of West Cermak Road. He was charged with two felony counts of robbery.
No further information was immediately available.