Zarif boarded the plane for the southwestern Kazakh city of Aktau, where the two-day event is to start on Sunday. He is heading a political and legal delegation.
The countries’ foreign ministers last met in Moscow in December 2017, agreeing on the text of the convention. The convention is slated to be ratified during the summit.
President Hassan Rouhani is also to attend the event.
Also joining the summit will be statesmen from the host country, Russia, Turkmenistan, and Azerbaijan.
The event is also expected to feature signing of six agreements between the maritime states on cooperation in the Caspian Sea.
The convention, which has been under discussion for more than two decades, would grant special status to the Caspian Sea, Russian Deputy Foreign Minister Grigory Karasin has told Russia’s Kommersant daily.
The status, he said, will be assigned based on the body of water’s “geographic, hydrological, and other features."
Concerning the marine resources, Karasin said, "The littoral states will have the full jurisdiction over resources in their sectors of the seabed."
The Caspian Sea is the largest enclosed body of water by area and is internationally considered as the world's largest lake or a full-fledged sea.