The 27-year-old Neymar was hurt in a 2-0 win over Qatar on Wednesday and was ruled out of the Copa America which starts on June 14 in Brazil.
"The two (club) doctors diagnosed a sprain of the lateral ligament of the right ankle without surgical indication, to be treated with conservative treatment," PSG said in a statement.
"The Paris St Germain striker is expected to return on the field in four weeks time."
Neymar has been accused by a woman of raping her at a Paris hotel last month, according to a police report.
He has denied the accusation which is being investigated by Sao Paulo police.
(Reporting by Julien Pretot; Editing by Ed Osmond)
