The Argentina international was absent from last weekend's win over Lorient due to an inflamed Achilles tendon, with Hugo Ekitike starting in his place.
Christophe Galtier's men scraped a 2-1 win without Messi in the ranks, but the seven-time Ballon d'Or winner has now been pictured with the ball at his feet in training.
As a result, Messi is expected to be involved in Sunday's game at the Parc des Princes in a major boost to Argentina before they take on Saudi Arabia, Mexico and Poland in Group C of the World Cup.
Messi has shone with 12 goals and 14 assists in 18 matches for the French champions so far this term, and Galtier affirmed at his pre-game press conference that no World Cup representative approached him with a request to be rested this weekend.
PSG also welcomed Presnel Kimpembe back from his own Achilles problem this week, but Spain midfielder Fabian Ruiz - who has not made Luis Enrique's squad - is still absent with a hamstring injury.
Galtier's side sit five points clear of Lens at the top of the Ligue 1 table and will be out to make it seven wins on the bounce in all competitions against AJA this weekend.