The crime happened at DeKalb Avenue & Flatbush Avenue in Brooklyn on September 29.
Investigators say shortly after 2:00 a.m. the suspect removed the victim's cell phone from a back pack that was on the floor between his legs.
When the train pulled into the station the suspect fled in an unknown direction.
The suspect is described as an 18 year old black man, 5'04" tall, approx 110 lbs. The suspect was wearing a black and gray sweatshirt, black pants and black sneakers.
Anyone with information in regards to the above incident is asked to call Crime Stoppers at 1 800 577 TIPS (8477). You can also submit tips by logging onto the Crime Stoppers website at WWW.NYPDCRIMESTOPPERS.COM or by texting tips to 274637 (CRIMES) then enter TIP577.
All calls are strictly confidential.