The Donegal native has asked his fans for their prayers after confirming that his wife, Majella, has been diagnosed with breast cancer.
In a statement on his official website, O'Donnell said: “I’m sorry to inform you that Majella was recently diagnosed with breast cancer.
"She is undergoing treatment at present and as it was found in the early stages we are very hopeful of a full recovery.”
The 51-year-old singer added: “I know that many of you would like to send your good wishes to Majella but at this time we cannot deal with a lot of mail.
"So we would ask you not to send cards or letters, all we need are your prayers to help us through this difficult time and we know we can rely on that.”