The 35-year-old made his return to the Camp des Loges training centre on Wednesday morning after achieving his lifelong goal of becoming world champion with Argentina in Qatar.
Messi received the Golden Ball as the tournament's best player, scoring seven goals and providing three assists, including a brace in the final as Argentina defeated reigning champions France on penalties.
Following La Albiceleste's global triumph, Messi was granted a lengthy break until the New Year, and he is understood to have flown back to Paris over the weekend.
The seven-time Ballon d'Or winner has now linked up with his Parisiens teammates once more, and both players and staff lined up to give Messi a guard of honour as he stepped out onto the training pitches.
After being congratulated by his teammates inside the building, Messi walked through the round of applause with a beaming smile before being presented with a trophy by football advisor Luis Campos.
The former Barcelona man is now being put through his paces ahead of PSG's Coupe de France tie with Chateauroux on Friday night, although he will not be expected to start against the third-tier side.
Messi's total for PSG now stands at 23 goals and 29 assists from 53 appearances since his arrival on a free transfer in 2021, including 12 goals and 14 assists from 19 games in all tournaments this season.
In Messi's absence, Christophe Galtier's side - who were also without the suspended Neymar - suffered their first defeat of the Ligue 1 season in a 3-1 beating at second-placed Lens on Sunday.
Przemyslaw Frankowski and Hugo Ekitike struck for both sides within the first 10 minutes, but further goals from Lois Openda and Alexis Claude-Maurice condemned the champions to defeat.
PSG still hold a four-point lead over Lens at the top of the Ligue 1 table and resume the defence of their title against 20th-placed Angers at the Parc des Princes next Wednesday