The 65-year-old TV presenter has been teasing for weeks that he is taking part in the ITV reality show at Gwrych Castle in north Wales, and signed off from the breakfast show with yet another clue.
Madeley told co-presenter Susanna Reid: "Now then... I've got places to go, people to see and things to eat... interesting things to eat, so I'll be back very soon after Christmas. This is my last show for a while.'
Reid quipped: "How do we say goodbye in Welsh? I don't know but I'm sure you'll find out in the next couple of weeks."
I'm A Celebrity is famous for its challenges which see contestants eating gruesome offal and insects in exchange for camp meals.
Madeley has previously hinted he will be taking part in the reality show — which last year moved from the Australian jungle to north Wales due to the coronavirus pandemic — by revealing he is learning Welsh.
His son-in-law — rugby player James Haskell, who is married to reality star Chloe Madeley — took part in the jungle show in 2019.
Madeley opened GMB by telling Reid, "I did say I'm going on a long drive tomorrow."
But he denied reports he is to become Piers Morgan's full time replacement on the breakfast show.
Addressing the claims in The Sun newspaper he told GMB viewers: "I think someone's put two and two together and got four and a half.
"I will be doing the show down the line, along with lots of other people."
An ITV spokeswoman said: “GMB is performing well with its established family of presenters and a rotation of guest presenters. There are no current plans to change this format.”
Earlier this year, Madeley said when asked about replacing Morgan full-time: "If the phone went and they said, ‘Would you come in and talk?’ of course I would talk to them. It would be bonkers not to.
"But I very much like sitting in for people. I have all the fun and very little of the responsibility or flak."
Morgan and Reid were known for their on-screen chemistry, often disagreeing over subject matters, and Reid would calm tensions in the studio after Morgan went on a rant.
Madeley presented This Morning with wife Judy Finnigan, 72, from its launch in 1988 until they departed to host their own Channel 4 chat show in 2001.
The couple were similarly known to clash amicably on screen and for Finnigan to step in when Madeley got riled when expressing an extreme opinion.
Watch: Will Gazza be joining Richard Madeley at the I'm A Celeb castle?