The long-running transfer saga has come to a close with the Iran international deciding to leave Osasuna after six years in Spain to head back to Tehran
The 31-year-old midfielder joins Esteghlal after six years with Spanish La Liga outfit Osasuna.
Osasuna were understood to be keen to offload Nekounam, who was their highest paid player, and according to Spanish reports he has left without any of his €2.5million buyout clause being paid.
The news is a major boost for Esteghlal, who finished the 2011-12 season in third place, having not won the Iranian title since 2009.
Esteghlal will be coached by Amir Ghalenoei this term and are also expected to unveil Farhad Majidi later in the week.
In other news, Osasuna's other Iranian Masoud Shojaei returned to playing action in midweek after a long spell on the sidelines with a foot injury.
Shojaei was a 71st minute substitute in Wednesday's 2-1 win over SD Huesca before playing half an hour in Friday's 3-2 triumph over SD Logrones. Shojaei has been sidelined for the past 15 months.