Between 2015 and 2025, Iran’s southeastern borders have faced a complex array of security threats, encompassing both internal and external factors. This study is qualitative and analytical in nature and employs a multi-level case study approach. By tracing the relevant processes, it seeks to map the evolution of security challenges and Iran’s strategic responses over the specified period. The central research question is: “What has been the national security strategy of the Islamic Republic of Iran in its southeastern border regions between 2015 and 2025, and which factors have influenced it?” The findings indicate that achieving sustainable security in southeastern Iran is only possible through an integrated strategy — one that simultaneously addresses the domestic roots of insecurity, such as poverty, ethno-religious discrimination, historical marginalization, and weak infrastructure, while also containing external threats, including instability in Afghanistan, the activities of terrorist groups, drug trafficking, and the interventions of regional powers. Within the framework of the Regional Security Complex Theory and the Copenhagen School, the research demonstrates that Iran’s national security strategy in this region has been a combination of “hard” measures (military and security operations) and “soft” approaches (developmental, social, and diplomatic initiatives). Ultimately, the study concludes that strengthening national security along Iran’s southeastern borders requires a participatory and data-driven approach — one that moves beyond the narrow securitization of issues and instead prioritizes the region’s socio-economic development and active regional cooperation.