Southbound train No. 264 struck the pedestrian at about 5:10 p.m. near Rengstorff Avenue, according to Caltrain spokeswoman Tasha Bartholomew.
Trains are being single-tracked through the area and commuters should expect delays of between 30 minutes and an hour, Bartholomew said.
The incident marks the fifth fatality involving Caltrain this year.
