Iran has been accepted as a founding member of the China-led Asian Infrastructure Investment Bank (AIIB), Chinese state news agency Xinhua reported late on Tuesday.
The decision was made by existing members, including China, Britain, France, India and Italy, it added.
The United Arab Emirates has also been accepted, Xinhua said.
The AIIB is seen as a potential rival to established lenders the World Bank and Asian Investment Bank, which are dominated by the United States and Japan.
China and Iran have close diplomatic, economic, trade and energy ties.