The 19-year-old had been working at a camp in Colorado and had been sleeping outside Glacier View Ranch, about 48 miles northwest of Denver.
He woke up at 4am on Sunday to a “crunching sound” and found the bear’s jaws digging into his head as the animal trying to drag him out of his sleeping bag.
The boy fought back, punching and hitting the animal as his colleagues woke up, realised what was happening and also tried to deter the bear.
Eventually, the animal gave up and walked away.
The boy, identified only as Dylan, was treated in hospital.