The Argentine was appointed on an initial 18-month deal to replace Thomas Tuchel as manager at Parc des Princes.
Pochettino had been out of work since being sacked by Tottenham in November 2019, just six months after guiding the club to its first-ever Champions League final.
His appointment marks his return to Paris exactly 20 years after he joined PSG as a player in January 2001.
“I am extremely happy and honored to become the new coach of Paris Saint-Germain,” Pochettino said, to the club’s official website
“I come back to the Club today with a lot of ambition and humility, while also being very eager to work with some of the most talented players in the world.