Alongside his blinding teeth makeover, which you can see in the video below, the 63-year-old has been sporting a dramatically different look over the last few months, frequently making headlines with his fresh-faced appearances – and it hasn't gone unnoticed by his colleagues.
According to The Mirror, during a media event ahead of BGT's premiere episode on Saturday, Dec told the audience: "We have a new face joining the judging panel."
To which Ant replied: "What? Simon has a new face?"
However, Simon has laughed off claims that he has gone under the knife and denied he has had any surgical help to achieve his new look.
DISCOVER: What is Simon Cowell's net worth?
"I think it's hysterical. I mean, it just makes me laugh. I haven't had a facelift or anything," he told the publication.
"I've had a bit of Botox or whatever, but nothing drastic. So, when I hear about this stuff, honestly it does make me laugh".
Simon's comments come after his appearance on ITV's Lorraine earlier this week sparked a huge reaction from viewers who claimed he now looks unrecognisable.
"Simon Cowell looks like a completely different person lately," one commented on social media. A second said: "Simon Cowell looks like a hologram."
A third added: "He seems to have changed his face which has made him look strange."
Simon's new appearance could be down to him leading a healthier lifestyle after a visit to his doctor made him realise he had to change his habits.
"I went to see this doctor in London, and we did some tests, and then a month later he said, 'You have the worst diet I've ever met from any patient'," Simon told Ellen DeGeneres last year.
Revealing how he improved his health, Simon explained everything he was forced to cut out of his diet. "It's pretty much all the things I loved that I can't now eat. So, no dairy, no sugar, no bread, no gluten, no red meat.
"I've gotta be honest with you, it was easier than I thought. And part of the reason I did it was because Eric is five this year so I realised that if I didn't sort myself out physically, I wouldn't be able to catch up with him."
Keep up with the latest celebrity stories Sign up to our HELLO! Mail newsletter and get them delivered straight to your inbox.