Dembele missed the first two games of the club’s Austrian training camp after suffering a knee knock but he got 45 minutes against the Czech side to put himself in the frame for Celtic’s European opener against Alashkert next Tuesday.
The French striker outmuscled his opponent and latched on to James Forrest’s pass down the right channel before firing a powerful strike inside the near post.
Manager Brendan Rodgers - who has been linked with a move for Hibernian midfielder John McGinn - told Celtic TV: “We had to ensure we nursed him through the game but he could have had a hat-trick. Probably a little bit of tiredness with a couple of his finishes but a great first goal - real strong, power and a great first touch.
“And [in the] first half him and Odsonne [Edouard] linked up really well. So it was good to have him back.”
It was a second friendly of the day for Celtic, who beat Austrian side BW Linz 2-1 in the morning thanks to goals from Mikey Johnston and Scott Sinclair.
Rodgers split up his squad with the aim of helping his players prepare for next week’s first qualifying round first leg in Armenia.
Leigh Griffiths, Marvin Compper and Scott Allan also featured for the morning team but Rodgers named a more experienced side for the afternoon encounter.
“It was a tough day for the players,” the Celtic manager said. “For the last 15 minutes of both games, you don’t get that in training when you are fatigued and trying to hold on to something.
“It was another excellent exercise for us and a really good end to the whole nine days.
“We couldn’t arrive into that game next week without having the full 90 minutes in the players’ legs. So that was the plan.
“It’s way earlier than we would like to but it’s a great credit to the players and the fitness and how they embraced it. Most of the squad, who we would say were the senior players, have got that.”
Jonny Hayes did not feature in either game after suffering a thigh strain during the weekend clash with Bohemians Prague.