**Background and Objective:** The legal regime of the Caspian Sea, with its ambiguities in border demarcation and legal framework, significantly impacts border interactions between Iran and Azerbaijan. The purpose of this study was to identify the consequences of the Caspian Sea legal regime on Iran-Azerbaijan border interactions.

**Method:** This applied, qualitative research collected data through semi-structured interviews with border experts, naval personnel, and academics. Data analysis was conducted with the participation of some respondents and using MaxQDA software to comprehensively and systematically extract basic and organizing themes.

**Findings:** Analysis of the interviews revealed 72 basic themes and 12 organizing themes related to the consequences of the Caspian Sea legal regime on maritime security, exploitation of shared resources, and security of the Iran-Azerbaijan maritime borders. These themes enabled a comprehensive and systematic analysis of the actual and potential effects of the legal regime.

**Conclusion:** The Caspian Sea legal regime has extensive consequences for Iran-Azerbaijan border interactions, resulting in operational limitations, increased security risks, reduced investment, and complexities in regional cooperation. The findings indicate that the absence of a clear and binding legal framework perpetuates misunderstandings, reduces mutual trust, and constrains sustainable development of shared resources. Therefore, formulating coherent policies and operational mechanisms, clarifying maritime regulations, and enhancing coordination among relevant agencies are essential for strengthening maritime security, optimizing the exploitation of shared resources, and improving maritime border management.