Comedian and actor says he can no longer play the guitar and banjo as Parkinson's affects the use of his left hand. Tremors and lack of mobility have meant he cannot play the instrument or the guitar, according to the Scotsman.
In an interview in Canada to promote his latest stand-up tour, he said: "I'm starting a documentary series in a month's time following the railways around America. I'm going to festivals and state fairs and all that.
"I've been longing to do it for a long time. The only trouble is that we're going to bluegrass festivals and I've got Parkinson's Disease and it's really affected my left hand and I can't play the banjo or guitar anymore, but I'll join in on the singing at least.
"It's been a rough go between that and the cancer. I kept telling my wife that haemorrhoids couldn't be far behind."
His wife, Pamela Stephenson, said in an interview last year that she had noticed her husband's hand shaking for many years, but assumed it was because he had spent too long playing the banjo, rather than a sign of Parkinson's.
She said: ''I've actually noticed his hand shaking for many, many years. I used to think he was playing the banjo a bit too much. I think it's been there for a long time.''
The 72-year-old is to travel around the United States by train for a new TV series. He will travel through 28 states and 8,000 miles later this year in new ITV documentary Billy Connolly's Tracks Across America.
When Connolly was on Desert Island Discs, he chose a banjo as his luxury item and also has a banjo tattoo on his left hand.
He revealed in 2013 that he had been diagnosed with Parkinson's and prostate cancer on the same day. Since then, he has been given the all-clear from cancer.