The Emmy-nominated presenter, who joins the This Morning team following the departure of Phillip Schofield and Holly Willoughby earlier this year, looked radiant in an off-white outfit and ritzy metallic shoes for her debut.
Cat is the much-loved host of So You Think You Can Dance in the US, but hasn't been a regular UK TV face for almost two decades - and her arrival left fans saying the same thing.
Cat, 47, teamed a sheer white blouse, complete with a pussy-bow neck tie, with a pair of fitted cream cigarette trousers and a matching waistcoat. Her expert layering exuded a timeless luxe aesthetic, made modern by her rose-gold Mary Jane heels.
The West Bromwich-born star elevated her understated glamour with delicate gold and silver accessories.
The presenter, who is married to RTE's The Late Late Show presenter Patrick Kielty, styled her honey-blonde hair in a vampy 70s-inspired blowout, letting face-framing bangs fall past her face.
Cat's stylish debut on the much-loved morning show was met with a united reaction from viewers, who took to X, formerly Twitter, to share their thoughts on her de-constructed suit.
"Oh Cat Deeley is fabulous on @thismorning… perfect with Rylan,so easy to watch. Great choice!" penned a fan, as another wrote: "Cat looks classy and timeless."
"Professional, classy, yet fun," quipped a third viewer.
Cat's This Morning debut comes just days after she stunned in silver at the Anine Bing Kate Tote cocktail launch in London last week.
The mother-of-one looked phenomenal in a silver slip dress, layered with a vampy leather jacket and chunky black boots, The star's metallic maxi dress looked incredible on her feminine silhouette, as she drew attention to her décolletage with a glittering silver choker.
In a previous interview with The Guardian, Cat lifted the lid on how she achieves her effortless aesthetic. "You begin to develop your style as a child. My mum let me wear whatever I wanted from a very young age, so long as I had an opinion about it," she said.
"Sometimes it would be the colour or print, but my main factor was whether the skirt was spinnable enough."