Greeting their reunion on Instagram, I'm A Celeb 2018 co-host Willoughby wrote a celebratory "Woooohooooo!" alongside three applause emojis.
Ant, 43, stepped away from TV roles in March, following his arrest for drink-driving.
The audience seemed to be looking forward to seeing the other half of the duo and went wild as Ant ran out on stage giving a bow.
Britain's Got Talent returns to ITV in April.
The simple snap showed the best friends and colleagues smiling as they sat in the back of their chauffeured vehicle.
But Holly herself confirmed that Ant will be back in the jungle.
Bowing to the screaming and cheering audience, before hugging Dec, McPartlin said: "Hello everyone. Make sure you look out for each other - we've missed having you around Ant, and hope you're feeling better in yourself now".
Filming began today on the 13th series of ITV's Britain's Got Talent with judges Simon Cowell, Amanda Holden, Alesha Dixon and David Walliams and presenters Ant and December. We missed you; it wasn't the same. "Shall we move on before I cry?"
The 59-year-old said: "Even though Dec was brilliant, it still wasn't the same".
He was driving while more than twice the legal limit.
Later that year, Ant entered rehab following struggles with a two-year addiction to strong painkillers as a result of a knee operation.
Lisa was employed as senior makeup artist for over a decade on Britain's Got Talent and today is the first BGT audition in 12 years that she hasn't been part of the show, .