Karamoko Dembele and Albian Ajeti both scored in the first half and although Conor Washington’s 77th-minute strike gave the Addicks hope of a comeback late on, Ange Postecoglou’s side held on for a second consecutive pre-season win.
The new Hoops boss added a bit more experience to his starting XI in Newport, bringing in Greg Taylor, David Turnbull, Nir Bitton, and Callum McGregor for their first involvement of the summer, with McGregor taking the captain’s armband for the first half.
Dembele and Adam Montgomery were tasked with working the flanks while Ajeti, Vasilis Barkas, Anthony Ralston, Ismaila Soro, and Stephen Welsh completed the line-up.
Ajeti nearly opened the scoring after just six minutes but saw his effort cleared off the line by Deji Elerewe after rounding the ‘keeper before Charles Clayden saw his cross-cum-shot deflected wide at the other end.
Birthday boy Turnbull then dragged a shot narrowly wide after receiving a pass from Taylor.
His central defensive colleague for the day Bitton then engineered Celtic's first goal, playing in Taylor whose cutback was met by McGregor and although Jason Pearce intervened, Dembele was on hand to net from close range.
Barkas then pulled off a fine save to deny Ben Dempsey an equaliser after good work by Albie Morgan and with five minutes until the interval, Ajeti doubled Celtic’s advantage, beating Scotland-qualified goakeeper Craig MacGillivary with a powerful header from Ralston’s cross.
Montgomery was the only player to start both halves, the winger being joined by ten new faces as Postecoglou rang the changes at half-time.
On came Scott Bain, Ryan Christie, Odsonne Edouard, Ewan Henderson, Leo Hjelde, Mikey Johnston, Dane Murray, Olivier Ntcham, Liam Shaw, and Osaze Urhoghide.
Henderson came close to teeing up Edouard but the youngster’s cross was just too far for the Frenchman to pounce, and the striker saw another effort blocked by former St Mirren loanee Akin Famewo on the hour mark.
Washington and James Vennings then had shots blocked by the Celtic defence as the English side sought a way back into the match.
Urhoghide set up Johnston with 15 minutes left but the winger’s effort smacked off the post and moments later Charlton went up the other end and reduced the deficit.
Josh Davison did well to pick out former Hearts striker Washington, and he nutmegged Bain to pull one back for Nigel Adkins’ side with 13 minutes remaining.
Celtic threw on Luca Connell and Owen Moffat and the latter sent in a teasing cross in the latter stages but there were no takers.
Bain then produced a fine one-handed save to deny Washington what looked like a certain equaliser in the dying seconds as Celtic ran out 2-1 winners.
Speaking after the game Dembele said: “It was good to get out there and play 45 minutes. I was pleased with my performance, and the goal, but the main thing for me was just being able to enjoy football again – I’ve not played for a while so when I’m out there I just want to show everyone what I can do.
"Now it’s all about working hard in training and trying to show the manager what I can do.”