The Greek international’s start to life in Glasgow has been disrupted due to injury, but he marked his first start by getting off the mark when he smashed home Anthony Ralston’s cross from close range on 35 minutes.
“I’m delighted for him. He hasn’t had an easy introduction to life here at Celtic, but I always felt he could make an impact for us,” said Celtic boss Ange Postecoglou.
“When a game is tight, he has physical presence in the box and took his goal well.”
Full-back Josip Juranovic added a second from the penalty spot with 10 minutes remaining as Postecoglou’s side extended their winning run to four games in all competitions.
Four sides are now separated by just a point at the top of the table as leaders Hearts were held 1-1 at home by Dundee.
Dundee United are now level on points with the Jambos and Rangers after beating Motherwell 2-1 at Tannadice.
Champions Rangers can go top if they avoid defeat away to St Mirren on Sunday.
Aberdeen ended a 10-game winless run and eased the pressure on manager Stephen Glass with a 1-0 victory over Hibernian thanks to Christian Ramirez’s goal at Pittodrie.