Rahmati won the Iranian league titles twice along with Sepahan of Isfahan.
The Esteghlal football officials have confirmed the transfer and announced that the player will pen his contract within the next few days.
Rahmati was a member of Esteghlal football team from 2005 to 2007.
The 28-year old keeper has played for Iran football team 58 times.
Traktorsazi of Tabriz defender Mohammad Nosrati has joined Esteghlal on a one-year contract.
Sepahan midfielder Ehsan Hajsafi also joined Traktorsazi of Tabriz on a two-year contract.