The 24-year-old caught a frustrated figure after his hattrick wasn't enough for France to retain the global trophy.
Argentina won the cup, led by his PSG teammate Lionel Messi – in a penalty shootout, despite his goals twice bringing the 2018 champions level.
However, although PSG players have been given 10 days off Mbappe was pictured at the French champions training ground.
? Reunion between @KMbappe and coach Christophe Galtier ?? pic.twitter.com/uGWg4eKdoQ— Paris Saint-Germain (@PSG_English) December 21, 2022
"Kylian Mbappe returned to training on Wednesday," tweeted PSG.
Mbappe, who finished top scorer at the World Cup with eight goals, was not expected back till January and PSG did not say whether he would be available for selection for their Ligue 1 match with Strasbourg on December 28.
His return to training comes the day after a documentary on France's campaign shows Mbappe giving his teammates a rousing halftime talk in Sunday's final following a limp first-half which saw them trail 2-0.
"It is the World Cup guys, it is the match of a lifetime!" says Mbappe in French broadcaster TF1's documentary.
"In any case we could hardly play worse than we have already done.
"We are going back on the pitch and either we carry on playing like idiots or we up the intensity.
"It is the World Cup Final! We are losing 2-0 but we can come back.
"Hey guys, this only comes around once every four years."
Although Mbappe led the fightback it took till the 80th minute – when he scored a penalty to make it 2-1 – for the team to really find the fighting spirit.
Mbappe was to go on and score his penalty in the shootout but, with Kingsley Coman and Aurelien Tchouameni both missing, Argentina were not to be denied, Gonzalo Montiel tucking away the winning spotkick.