This study examines the challenges of managing transboundary water resources between Iran and neighboring countries, especially Afghanistan and Turkmenistan. The challenges under study are rooted in historical, geopolitical, legal, and environmental factors and have been exacerbated by climate change and increasing pressure on water resources. Border rivers such as the Hirmand, Harirud, Atrak, and Tajan, despite their vital role in providing water to the eastern and northeastern regions of Iran, have become the focus of international tensions due to the construction of dams (such as the Kamal Khan Dam in Afghanistan), the ineffectiveness of existing treaties (such as the 1973 Hirmand Treaty), and the lack of attention to the principle of equitable and reasonable utilization (ERU). The present study, relying on the theoretical frameworks of “Integrated Water Resources Management” (IWRM) and “Hydrodiplomacy,” proposes solutions to reduce these tensions. The most important recommendations include strengthening regional cooperation through the establishment of basin-based institutions (IRBOs), modernizing water management practices with new technologies, revising legal treaties with regard to climate change, and promoting multi-level stakeholder participation. Local capacity building, adaptation to the consequences of climate change, and equitable distribution of water are also emphasized as key pillars of sustainability of shared resources. The findings show that resolving transboundary water crises requires a comprehensive approach, based on active and flexible diplomacy. This study highlights the importance of regional integration and transformation in water governance as an inevitable necessity for Iran’s water security.