A crew member on northbound train No. 151 called for medical assistance at about 2 p.m. after a passenger was found unresponsive when the train stopped at the Hillsdale station, Caltrain spokeswoman Tasha Bartholomew said.
When emergency personnel arrived, they found a 61-year-old man dead on the train, Bartholomew said.
The man couldn't be removed until the coroner arrived, so train No. 151 was canceled and those passengers were transferred to northbound train No. 155.
Trains single-tracked around train No. 155 until it was removed and the track reopened at about 3:25 p.m.