The woman was pulled from the under the train, alive, after she was trapped at about 10:30 p.m. Saturday, BART spokesman Linton Johnson said.
Officials didn't know how the woman had gotten trapped under the train, which was heading to downtown Oakland, Johnson said.
Emergency personnel were able to separate the train cars and extract the woman. She was on her way to a local hospital at about 11:10 p.m., Johnson said.
He declined to release the woman's condition.
After the incident, the Rockridge station was closed until about 12:15 p.m., Johnson said. Prior to that, trains were single-tracking through the station but weren't stopping.
No service delays were reported, Johnson said.