Jimmy Kimmel's son is ''doing great'' after undergoing heart surgery in 2017.

Billy, now two, underwent open heart surgery just days after he was born in April 2017, and the 51-year-old talk show host - who has Billy, as well as five-year-old Jane, with his wife Molly McNearney - has said he's in good health two years on from his major operation.

Jimmy told Us Weekly magazine: ''[Billy is] doing great. He thinks he's Spider-Man now, so we're safe from crime. He wears the costume all the time. He's shooting webs all over the house.

''He goes to preschool as his secret identity and then turns into Spider-Man when he comes home.''

The 'Jimmy Kimmel Live' star - who also has kids Katie, 28, and Kevin, 25, with former wife Gina - announced the news of Billy's surgery on his talk show at the time, and said waiting for the operation to finish was ''the longest three hours'' of his life.

He said: ''On Monday morning, Dr. Vaughn Starnes opened his chest and fixed one of the two defects in his heart. He went in there with a scalpel and did some kind of magic that I couldn't even begin to explain. He opened the valve, and the operation was a success. It was the longest three hours of my life.

''He's doing great. He's eating. He's sleeping. He peed on his mother today while she was changing his diaper. He's doing all the things that he's supposed to do. This is the best.''

And last year, Jimmy took to social media to mark Billy's first birthday, where he also took the time to thank the medical staff who had ensured the tot's survival.

He wrote: ''A yr ago today, God gave us this tough little boy. Today, we thank the nurses & doctors at @CedarsSinai & @ChildrensLA who saved his life & those who shared thoughts & prayers. We cannot stay quiet. Please wish Billy happy birthday by REGISTERING TO VOTE! https://vote.gov (sic)''

Jimmy previously admitted he didn't want to ''get too close'' to his son after he was born with the congenital heart defect.

The TV star and his spouse weren't initially open with their feelings about the situation, but realized after the tot had undergone a second surgery they had shared the same fears.

He said: ''There were secrets we kept from each other that we revealed only after the second surgery.

''The biggest one was that, I think subconsciously, we didn't want to get too close to the baby, because we didn't know what was going to happen...I don't know if that's right or wrong or common or uncommon.

''But when I told her I was feeling that way, she said, 'Oh, I'm so happy you said that because I was feeling that way too, and I didn't want to express it.' ''