Both Mbappe and Neymar scored one and set up two other goals as the French champions, who had already made sure they would end the group phase on top, finished with 16 points, five ahead of Real Madrid after the 13-time champions beat Club Brugge 3-1 away.
PSG and Galatasaray fans clashed briefly before kickoff outside the stadium with one supporter being taken to hospital with a minor injury, a police source said.
Neymar played Mbappe through and the French international flicked the ball into the path of Icardi who poked home the ball to put the hosts ahead with his fifth Champions League goal this season — his 12th in his last 13 games in all competitions.
Sarabia made it 2-0 three minutes later with an angled shot after being set up by Neymar. The Brazilian found the back of the net himself two minutes into the second half with a left-footed strike into the far corner after being set up by a Mbappe backheel.
Mbappe, who has now scored 19 goals and set up 11 in 30 Champions League games, increased the advantage in the 63rd with a cool finish from another Neymar assist.
Fan favourite Cavani, who came on as a second-half substitute, rounded it off with a penalty in the 84th minute after Ryan Donk had brought down Mbappe.