The comedian features on tracks on the record by Northern Irish songwriter and music producer Phil Coulter.
The Big Yin plays the autoharp on the Irish-themed album called Echoes of Home which is released later this month.
The 71-year-old started his career in folk band The Humblebums with the late songwriter Gerry Rafferty before turning to comedy.
Coulter, 72, was Connolly's record producer in the 1970s and the pair have remained friends ever since.
The musician, who has also worked with Sinead O'Connor and Van Morrison, told how he was delighted to get Connolly on board.
He said: "He has never lost his passion for folk music or for the banjo, just like his buddy Steve Martin."
Last September, Connolly announced he had had surgery for prostate cancer and was being treated for early symptoms of Parkinson's disease.