In the past few decades, Iran has faced a severe water crisis. The Hirmand river basin, which extends from the southwest of Afghanistan to the east of Iran, has been the site of successive conflicts between the two countries for nearly a century, but these tensions have subsided in recent years following the spread of the water crisis in Iran and the construction of a dam in Upstream Afghanistan has become more prominent. As a country that is located in the downstream part of many of its important river basins, Iran's relations with its upstream neighbors, including Afghanistan, play an important role in access to water. Iran and Afghanistan have two common river basins, the Harirud river basin and the Hirmand river basin. The Hirmand river basin is the only transboundary river basin of Afghanistan and Iran, whose official agreement is the Hirmand River Treaty of 1973. In this way, in our opinion, the leading study is an interesting case to examine the water relations between Iran and Afghanistan. Our research indicates that transboundary water resources in the Hirmand river basin have been politicized and even security by Iran, no study has investigated how Iranian government officials have considered water as a political and security issue. This study suggests that spatial scale, water scarcity, and socio-political context are important factors shaping security in Hirmand river basin.