The collision was reported at 3:11 p.m. Thursday near California and Fillmore streets.
The 91-year-old woman apparently tried to go around the truck but was struck and suffered major injuries. She was taken to San Francisco General Hospital, where she was later pronounced dead, police spokesman Officer Albie Esparza said.
The woman's name is not yet being released by the medical examiner's office.
The truck's driver stopped at the scene and cooperated with investigators, Esparza said.
The collision remains under investigation, he said.
The death is the fourth involving a pedestrian in San Francisco so far this year. There were 21 such deaths reported in the city in 2013.