The 53-year-old confirmed the news saying it was "exciting and quite an honour to be asked".
"There's so many people that could be asked," he added.
"I don't know if I'm as good as I need to be but I'm going to try. There's a lot of rehearsals and physical work which I'm not used to.
"I can dance but don't ask me to be in a certain place at a certain time, this is going to be very hard for me. God help whoever gets me!"
O'Donnell has had a string of hit albums in both the UK and the US since the mid-90s and a very loyal fan base.
He revealed he is a huge fan of the show and has been asked to take part in the Christmas special several times, but has always been too busy touring.
O'Donnell told how his wife recently battled cancer and he consulted her about whether he should sign up to the show because it is a big time commitment.
He revealed: "She said, 'You can have time off any time, don't miss this.'"
So far seven other celebrities have been confirmed - singer and reality star Peter Andre, BBC weather presenter Carol Kirkwood, celebrity chef Ainsley Harriott, broadcaster Jeremy Vine, former Coronation Street star Georgia May Foote, EastEnders actress Kellie Bright and newsreader Katie Derham.