Andrew Meunier had been letting his dog out in Naples, Florida, on Tuesday night when he saw the animal just a few feet away.
The bear, standing about one metre tall, was staring him down.
Mr Meunier told WZVN TV: "It was standing in front of me and I tried to turn left real quick and get back in the house and caught an uppercut from a brown, or black, bear."
Mr Meunier, 41, sustained a number of cuts, including a large one on his face, which later needed fours hours of surgery and 41 stitches.
He escaped the bear and managed to get back into his house through the front door.
"I'm just happy to be alive," he said.
"It could have been a totally different story."
Traps are being set up to catch the bear, local media reported.
This is thought to have been the first bear attack in south Florida since 1970, although residents near Mr Meunier's home say they have seen bears going through rubbish bins.