The French forward underwent tests after being forced off during Les Parisiens 1-0 Coupe de France victory over Saint-Etienne on Friday.
Loic Perrin’s reckless challenge forced Mbappe off the pitch, with the French side revealing the extent of the injury to his right ankle.
“As announced after the final of the Coupe de France against Saint-Étienne, Kylian Mbappe underwent further examinations to his injured right ankle,” read a statement on the club’s website.
“The results of today’s scan confirmed an ankle sprain with damage to the external ligament. The player is expected to be sidelined for approximately three weeks.”
As a result Mbappe will miss PSG’s match with Atalanta set for August 12 in Lisbon.