"They look at him and see how small he is and they say, 'Awesome, the little guy can hit a golf ball,'" the boy's father told Fox 29.
"And then they look and they see that he's doing it with one hand and they say, 'That's incredible."
Doctors believe that Tommy Morrissey's right arm didn't develop below the elbow due to a blood clot.
Tommy began watching golf YouTube videos with his father Joe when he was just 13 months old.
"He'd watch it as though he understood what was happening," his mother Marcia told Golf Digest.
When he was 18 months old, Tommy began mimicking the actions of the golfers in the videos, so Joe and Marcia gave him a plastic golf club and ball to play with.
They were impressed with how quickly he mastered the art of a golf swing and it wasn't long before Tommy was joining his parents on trips to their local golf club in New Jersey, US.
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"My husband plays golf and I play golf," Marcia said. "Thomas became obsessed with it. He started watching YouTube instruction all on his own, mostly Bubba Watson, really. So we began nurturing his obsession. It's unreal."
Marcia added that doctors at Shriners Hospital in Philadelphia predicted that Tommy would develop exceptional hand-eye co-ordination.
"His body and his brain think he's right-handed, but without a right hand his brain has to compensate in ways yours and mine would not," she explained.
Tommy's advice for grown ups who want to try to out drive him?
"Grip it and rip it."