Umtiti has played with Neymar at Barcelona and with Mbappe for the French national team, and believes that PSG will be unstoppable with both players in their side.
Speaking to 'Canal+', Umtiti said: "Neymar was a very good team-mate to have when he was at Barcelona.
"He's somebody who is always full of joy, who is always happy and who is always playing pranks and making jokes.
"We know all about Neymar's qualities. He can unlock any match. He is [playing] at an exceptional level.
"Neymar together with Kylian Mbappe ... players of their talent are made to play together. There is no reason why it should not work.