The main objective of this study is to examine the impact of the expanding presence of Afghan nationals on the security of the Islamic Republic of Iran, especially after the Taliban came to power. This study aims to examine the effects of this presence on Iran’s political, economic, cultural, and social security. The main research question is how the increase in the number of Afghan immigrants can affect the country’s security. Sub-questions examine specific threats in the political and economic spheres as well as cultural and social challenges. The main hypothesis is that the widespread presence of Afghan nationals, along with the increase in extremism and terrorist threats, can lead to security problems in Iran. In this thesis, using theoretical frameworks related to national security and migration (Copenhagen School), the available data is analyzed. The findings show that the increase in the population of Afghan immigrants in Iran can bring about several challenges, including pressure on economic resources, increased social tensions, and cultural threats. Also, political threats resulting from the possible influence of extremist and terrorist groups have been examined as an important factor. Finally, solutions have been proposed for better management of this situation and reduction of security threats. The present study is of the realist type and the qualitative research method is documentary. In this study, library and document collection methods, examination of documents and records, interviews with experts and experts on the subject were used to collect information and it was analyzed using the analytical-descriptive method. According to the findings of the study, it was concluded that the expansion of the presence of Afghan foreign nationals in the Islamic Republic of Iran after the Taliban came to power indicates that the effects of this presence can be effective on political, economic, cultural and social security.