The Brazilian was stretchered off the pitch during the Ligue 1 outfit's 3-0 victory over Marseille on Sunday.
Concerns have been centred around the attacker's availability for next week's Champions League last-16 second leg against Real Madrid, and now it appears that the former Barcelona star will be on the sidelines.
PSG have not given a timeline of recovery, but they have confirmed in a statement that Neymar suffered a severe sprain to his right ankle and his fifth metatarsal has been fractured.
The French club already have a mountain to climb in the Champions League ahead of the showdown at Parc des Princes as they are already 3-1 down from the first leg.
The Brazilian has scored 29 times in 30 appearances in all competitions for PSG this season.