In the 21st century, transboundary water management and policymaking have become among the most critical strategic challenges for nations. The Helmand River, as one of the most vital water resources in southwestern Asia and the main artery of Lake Hamun, plays a key role in the political and security relations between Iran and Afghanistan. The link between water rights and national security has led to the process of “securitization” of transboundary waters. This study, adopting a water security management and policy approach and grounded in securitization theory, examines the formation and management of tensions related to the Helmand River’s water allocation and proposes strategies to enhance international cooperation, reduce security tensions, and promote sustainable water management. The research employs a combination of content analysis and discourse analysis of national and local officials in Iran and Afghanistan to identify linguistic patterns and decision-making processes influencing the securitization of water. Findings indicate that Iranian governance actors, through managerial and security discourses, have redefined the Helmand River as a component of national security, and the proposed management strategies can contribute to improving water security and sustainable regional development.