The incident happened shortly before midnight near Chapel Avenue and Valley Boulevard, according to Alhambra police.
Authorities said the truck was backing into a Taco Bell restaurant for a delivery when the car, traveling westbound, crashed into it.
The driver of the sedan was transported to a nearby hospital. His or her condition was not known.
The intersection was temporarily closed as authorities investigated the scene. All lanes were back open at 6:30 a.m.