The pair will host the show from next month, replacing previous presenters Philip Schofield and Holly Willoughby, who left the show last year.
Deeley and Shephard who had previously presented the show on separate occasions, will host the show from Mondays to Fridays, with Dermot O'Leary and Alison Hammond hosting the flagship show on Fridays.
"This Morning is a national institution. Whenever it's on, it’s like having your friends over – funny, smart, silly, heartfelt, informative and joyful – like all the greatest friendships!", Deeley said in a statement.
Deeley continued, "This Morning is and always will be the viewer’s show. Ben and I both know how much people love it, and with the help of an amazing team of people, we’re going to do our best to take care of it".
Ben Shephard also added, "This really feels like a very special moment for Cat and I to be part of the next chapter of This Morning. It’s an honour to be trusted with the reins, join Alison and Dermot and all the team that work on and off screen and do such a great job".
"For the last 10 years I’ve been waking up with our ITV daytime audience on GMB and I now look forward to spending time with Cat, welcoming the viewers home after the school run or from their early morning routines, with a cup of tea and a mix of everything that makes This Morning so loved".
Cat Deeley has previously hosted ITV show Stars In Their Eyes, as well as BBC's Fame Academy, as well as American show So You Think You Can Dance. Ben Shephard has previously presented Tipping Point on ITV, and Ninja Warrior UK.
Cat Deeley is married to Late Late Show host Patrick Kielty, with the couple based in London, having previously lived in California.
