The former Barcelona academy player joined PSV on a five-year deal from PSG last summer upon the expiry of his contract.
Sources have told ESPN the deal to return to PSG includes a re-sign clause of €12 million ($13.5m).
"Xavi Simons immediately leaves the training camp to complete the transfer with Paris St Germain," PSV said in a statement.
Simons spent most of his youth career at Barcelona before leaving to join PSG in 2019. He made his professional debut in 2021 and played a part in the club winning the Ligue 1 and the French Cup later that season.
After moving to the Netherlands, Simons helped PSV secure a second-place finish in the Dutch top flight, making 34 appearances, scoring 19 goals and registering eight assists.
He has won the KNVB Cup, Johan Cruyff Shield and Eredivisie's top scorer award during his time at the club.
"The twenty-year-old attacker came to PSV last year and became an important player in Ruud van Nistelrooy's team," the club added.
Information from ESPN's Julien Laurens contributed to this report.