The Riveside County Coronerâ€™s office identified him as a 41-year-old from South Hadley, Mass., but his name has not been released.
According to authorities, the truck hit him about 4 p.m. on northbound Highway 111, 372 feet south of the Salt Creek Beach campground.
He was airlifted to Desert Regional Medical Center in Palm Springs, where he was pronounced dead at 5:50 p.m.
The driver of the truck stopped at the scene and cooperated with investigators, the California Highway Patrol reported shortly after the crash.
There were no road closures.
Other details were not released.