Troopers said friends and family were driving back to Salt Lake City from Wendover when the tired driver fell asleep and veered off the road on I-80 westbound at the Tooele County and Salt Lake County line just before 7 a.m.
The passenger in his 30s who died was lying down in the backseat, not wearing his seat belt, when the car went off the road and flipped over a barrier.
Officials said a second car with family members was driving back with them but no one was injured in that vehicle.
The freeway was at a standstill until after 8 a.m. when crews were able to clear the scene.
The names of those involved have not been confirmed at this time.