The incident happened shortly before 11 p.m. Sunday on the on-ramp from southbound Highway 99 to eastbound Highway 180.
CHP officials say a total of three vehicles hit a pedestrian. That person, who has not been identified, died at the scene.
Authorities say it's unclear how the victim ended up on the highway. "We do not know how the pedestrian came to be on those traffic lanes. There is no crosswalk or anything of that sort at that location," said Jose Nunez, California Highway Patrol.
Authorities say the drivers of all three vehicles stopped to help with the investigation and no charges are expected to be filed.
The onramp involved in the accident was closed for hours, but has since been reopened.