Daevonn Hartley was struck at about 2:30 p.m. by a train headed to the East Bay.
Emergency crews responded and were able to extract Hartley, who was taken to San Francisco General Hospital where he succumbed to his injuries at 7 p.m., according to the medical examiner's office.
BART spokesman Linton Johnson said this was the second suicide attempt on BART tracks this year and the first to turn fatal.
The incident caused major delays throughout much of the BART system for more than an hour Wednesday afternoon.
