It happened before 7:30 pm on Highway 180 near San Benito Road.
CHP officers said a Chevy Silverado was westbound on the highway when the driver suddenly drifted into the opposite lanes.
The Chevy collided head-on with a big rig.
Officials said the driver of the Chevy is a Mendota man in his 60s. He died at the scene.
The big rig driver was not hurt.
It's unclear if drugs or alcohol were factors in the crash.