The deer was struck at about 10:30 p.m., slightly damaging the front car of the train, BART spokesman Jim Allison said.
The train stopped after striking the animal. Another train came and was attached to the stopped train. All passengers in the damaged first car were moved to another part of the train, and the damaged car was taken away to a BART maintenance yard for repairs, Allison said.
The striking of animals on the tracks is "not totally uncommon," he said.