The Daybreak star, who defected to ITV last year, will co-host the 2012 series alongside Phillip Schofield.
Bleakley said in a statement: "I've always been a total Dancing on Ice addict so it really is hard to sum up how excited I am to be joining the team.
"My only concern was what a big task it is to follow the brilliant Holly and I can only promise her, Phillip and everyone at home that they couldn't have a bigger fan of the show on board."
Schofield, who works with Willoughby on This Morning, commented: "I'm absolutely delighted that Christine is on board and I'm really excited about the new series."
Willoughby tweeted: "Good luck to Christine Bleakley on this year's Dancing on Ice. It's a truly magical show and you will love it. I'll miss you all very much!"
She quickly added: "No.... I'm not pregnant!"
There has been speculation that Willoughby's departure coincides with a new presenting role on BBC One's upcoming talent show The Voice, but nothing has been confirmed.
Dancing on Ice is expected to return for its seventh series in January.
> Dancing on Ice to get '360-degree seating arena'