The 22-year-old Argentina international moved to Ligue 1 in a reported €42 million (£36m) deal, and life in France has started brightly for Pastore, whose side lead the championship race.
Messi, who is currently on international duty along with 'El Flaco', hailed the ex-Palermo man and said moving to France was a good choice.
"Pastore was wanted by a number of big clubs, but Paris are building a great team now and Pastore has great qualities. I am sure he will progress at PSG," Messi told Canal Football Club.
"I think playing in France is difficult, but this will help him."
Argentina take on Colombia in a World Cup South America qualifying match on Tuesday night.
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