The 31-year-old player left Iran in January after Esteghlal failed to meet its financial commitment.
Milic is reportedly going to extend his contract.
Milic had been sidelined by ex-Esteghlal coach Mahmoud Fekri for several matches but newly-appointed coach Farhad Majidi has a good relationship with the Croat.
Esteghlal sits third in the Iran Professional League table.