Afghanistan is a country located in the east of Iran and has had ups and downs in relations with Iran throughout its history. Geographical proximity and historical relations have meant that no other country can play a more important role than Iran in Afghan society. In this context, the two countries have had various relations in the political, economic and security spheres over the years. Hydropolitical disputes, drug trafficking, illegal immigrants and the presence of ISIS Khorasan terrorist forces, along with economic and cultural cooperation, are among the most important issues between the two countries during this period. In this regard, the main question of the research is posed as follows: What impact have the developments in Southwest Asia had on Iran's relations with Afghanistan? In response to this hypothesis, it is proposed that despite the civilizational, cultural proximity and economic cooperation between Tehran and Kabul, given the zero-sum situation as the governing principle of geopolitical developments in Southwest Asia, especially after the Taliban came to power in 2021, threats such as the refugee crisis, drug trafficking, the presence of the ISIS Khorasan terrorist group, and the issue of sharing the Helmand water or hydropolitical disputes have increased tensions in Southwest Asia, especially between Iran and Afghanistan. We conduct this study based on a descriptive-analytical approach using the trend research method and sample study as qualitative research methods, which used documentary-library sources and reliable cyberspace websites to collect information.