The woman was standing near the Green Line platform about 8:15 p.m. in the 200 block of South Wabash Avenue when a male juvenile approached her, Chicago police said.
Police say the attacker punched the woman and she fell to the ground. The juvenile took her cell phone and ran off, but he was arrested in the 400 block of South Plymouth Court, police said.
The victim was transported to Northwestern Hospital in fair condition, police said.
Charges were pending.