The 30-year-old Gabonese midfielder currently plays for the Saudi Arabian club Al-Riyadh.
Ndong has been a member of the Gabon national football team since 2012.
He started his playing career in Tunisian club CS Sfaxien in 2011 and has also played for English sides Sunderland and Watford.
Esteghlal has previously reached an agreement with French winger Gael Kakuta.