The X Factor presenter will host the daytime show for the first time alongside Holly Willoughby, as he fills in for Phillip Schofield.
Phillip will be away for one week to film a new series of ITV game show, The Cube, and what better replacement than Dermot?!
"I'm delighted to be guest hosting TM for a week," Dermot said. "When Holly called me and asked, I couldn't resist, I really miss working with her and am looking forward to having some fun."
Dermot previously worked alongside Holly when she hosted The Xtra Factor in 2008 and 2009.
"I'm a huge admirer of Phillip, so to be asked to stand in for the great man is indeed an honour - I can't wait," Dermot added.
Adam Vandermark, editor of This Morning said: "I'm thrilled Dermot will guest host in the New Year and is so passionate about doing it. He and Holly have great chemistry which is no surprise because they are such good friends."
After Dermot's guest stint, he will go on to host the annual National Television Awards.
Other guest presenters who have stepped in on This Morning include, Myleene Klass, Ben Shephard, Jenni Falconer and more recently, Marvin and Rochelle Humes, who completed their second stint on the show last month.
Dermot will co-host This Morning during 13 - 16 January 2014.
Subscribe to Reveal Mag for Android & Apple devices just £2.49 for 4 issues! Check out how fab it is in the promo below!