The sons of legendary Australian singer John Farnham have revealed that their dad "got all teary" when he heard of the outpouring of support since announcing his cancer surgery.

"He never expects everyone to still love him, but they do. So thanks, pretty much, everyone" James Farnham, 34, told A Current Affair.

Robert and James expressed how grateful the Farnham family was to the doctors, nurses and everyday Australians who have supported them over the last few months.

"It was beautiful to see the amazing messages. It's a strange thing, everyone just feels that they are a part of it, if that makes any sense. But it's a good feeling," Robert, 41, said.

"We can't say enough how much we thank all the nurses and all the doctors. They did such a good job at putting him at ease and putting us at ease."

John underwent surgery to remove a cancerous growth on his mouth on August 23. After surgery, John spent time in a rehabilitation centre as he began to heal.

"He is in recovery now. He pulled through the surgery. That was hectic. Pretty hairy," Robert said. "He was having trouble sleeping," James said.