The person was struck around 4 p.m. at the station, located at 2901 Diamond St., BART spokeswoman Alicia Trost said.
Medical personnel responded and pronounced the person dead at the scene minutes later, Trost said.
Authorities are investigating the incident. The station was closed as power was turned off on the northbound rail line and trains were single-tracking through the station on the southbound tracks, Trost said.
BART officials announced shortly after 6 p.m. that the Glen Park station had reopened.