The Brazil international has been ruled out for up to eight weeks after picking up the injury against Saint Etienne in Ligue 1 on Sunday.
Neymar had to be stretchered off following a challenge from a Saint Etienne player late in the second half.
PSG defeated Saint Etienne 3-1 to move 12 points clear at the top of the Ligue 1 standings but that victory has come at a cost for Mauricio Pochettino’s side.
PSG have said in a statement on the club's official website: "The examinations carried out confirm that Neymar Jr suffers from a sprained left ankle with ligament injuries.
"An unavailability of 6 to 8 weeks is to be expected. A new assessment will be made in 72 hours to specify the recovery."
"Unfortunately, these setbacks are a part of an athlete’s life," Neymar wrote on Instagram after the match.
"Now you have to raise your head and move on. I will come back better and stronger."
Neymar has made 14 appearances in all competitions for PSG this season, scoring three goals and providing three assists.
