Iran shares a 954-kilometer border with Afghanistan to the east. Any change in Afghanistan's domestic andforeign policy and the decisions of the ruling government regarding relations with its neighbors will affect the geopolitics and security of the region. Recent developments in Afghanistan, which have been accompanied by the overthrow of Ashraf Ghani's government and the rise of the Taliban, have led to disruption in the geopolitics of the region and are affecting the national security of the Islamic Republic of Iran. How to use and manage common water resources has become a contentious issue in the relations between the countries upstream and downstream of the common rivers. Water disputes have also been influential in the foreign policy of countries in opposition to each other. Iran is no exception to this rule due to its common rivers. The purpose of this study is to investigate the impact of political developments in Afghanistan on border hydropolitics and environmental security policies of the Islamic Republic of Iran and seek to answer the question of the recent developments in Afghanistan. On the border hydropolitics and environmental security of the Islamic Republic of Iran? The results showed that the lack of efforts for joint cooperation in the field of border hydropolitics between Iran and Afghanistan leads to environmental consequences including the extinction of the habitat of Hamun and Lake Hamun, the loss of fish, bird migration, drought and dust, migration And reducing the income of the people of the region and the smuggling of drugs,