The California Highway Patrol says a Toyota Tacoma was going west on Highway 180 at about 5:30 a.m. when it went through the guardrail.
The truck landed below on Highway 41.
The passenger was taken to the hospital, where he died.
The driver was also injured, but is expected to recover.
Officers say the rainy weather was a factor in the crash with slippery conditions.
Drivers are urged to be cautious on the roads as storms move across Central California.