Afghanistan is a land-locked country that depends on its neighboring countries to transit essential commodities. Iran, for its proximity and access to the high seas, seems to have the most economical route to meet Afghanistan’s needs. However, this country did not pursue such an economical route due to its western tendencies and its foreign policies which were completely different with Iran’s. The international relations of the countries in the region were extremely affected by the Cold War during the 2^nd Pahlavi era from 1941 up to 1978. After World War II and the emergence of Pashtoonistan subject, and due to remoteness of Russian routes and their high costs, Iranian routes were the best for Afghani goods to be transited.  This research, depending on documents relating to this time, is going to clarify how the improvement of transit routes of two countries led to the development of their economic relations and coming to bilateral treaties in this field.