Ant has spent time in rehab in the USA for his addiction which developed following a botched knee operation in 2014.
The 41-year-old has also faced speculation his marriage to Lisa Armstrong is under increasing pressure after Ant confessed he'd put his wife "through hell" during his addiction struggle.
Speaking about his return, Ant recently said: "I'm excited to be back, I can't wait, ' says Ant".
Ant and Dec have arrived in Australia for I'm A Celebrity Get Me Out Of Here. "I'm feeling great". Great to hear it!
Dec, 42, was delighted to be reunited with his friend.
'Everything just slotted back into place.
Ant and Dec will return to present the celebrity survival challenge, as another batch of famous faces are flown out to the Australian jungle, where they can look forward to completing the usual round of tough daily tasks and dreaded Bushtucker Trials until one of them is chosen as this year's King or Queen.
"We'll have the same old shenanigans, but with a few little added twists". Get Me Out Of Here returns this Sunday on ITV, and it's going to be a tough start for the celeb contestants. "We've been waiting for ages, it's been a long summer break so we can't wait".
Childhood sweethearts Ant and Lisa have been together for 23 years but last month, he moved out of their marital home into rented accommodation nearby.
Addressing rumours that all isn't well with their relationship, she tweeted: '#writewhatyouwant #haventbeentoOzfor10years #ihaveajob #allaloadofmadeupshit #imnotestrangedthank-you #asyouwere'.
Later Ant, who was wearing his wedding ring, stripped off by the pool and puffed on a cigarette.