Thiago Silva out of action for three weeks
The Brazilian had to be replaced in the 57th minute of Friday's 0-0 home draw against Ajaccio after he picked up the injury when landing on his leg.
"The MRI he underwent today has confirmed he has suffered a femoral muscle problem in his left leg," PSG said on their website.
"He will be out of action for at least three weeks," added the French club, who will play their Champions League last 16 first-leg at Spanish side Valencia in four weeks.
The 28-year-old Silva, who joined from AC Milan in the off-season for a fee of 42 million euros plus five million in adds-on, is expected to miss at least three league games for second-placed PSG and their French Cup last 32 tie against Toulouse.
The Brazilian, widely regarded as one the world's best defenders, has quickly established himself as PSG's leader in the backline and was handed the captain's armband in November.
He has played 15 Ligue 1 games and was key in helping PSG top their Champions League group ahead of former winners Porto, playing the six games and scoring two goals.