It happened around 7:30 p.m. Monday.
Officials say a Paoli/Thorndale train was heading into Wynnewood from Ardmore, when a woman was spotted on the tracks.
The train operator sounded the horn and applied the emergency brake but the train was not able to stop in time.
The woman was struck and pronounced dead at the scene. No word on her identity or why she was on the tracks.
SEPTA officials say the Paoli/Thorndale line may experience delays of up to 30 minutes due to police activity.