The present study examines the geopolitical challenges of exploiting oil and gas resources in the Caspian Sea between Iran and Turkmenistan. The primary research question is what factors underlie the energy differences between the two countries and whether these differences are solely due to legal issues or are also influenced by national interests and pressure from transregional actors. The research hypothesis is based on the fact that existing geopolitical challenges are the result of a complex interaction among the legal structure, conflicting national interests, and competition between regional and transregional actors. The research method combines analytical and qualitative approaches, utilizing document content analysis and a review of specialized books and articles. Data were collected from written sources, agreements, Caspian conventions, and scientific articles and were examined based on three levels of analysis (structural, national and regional, and transregional). The findings show that the Caspian’s legal ambiguities, the pressure of sanctions and internal Iranian restrictions, Turkmenistan’s export strategies, and the influence of Russia, China, and the United States have all contributed to the persistence and intensification of disputes. These results confirm the research hypothesis and indicate that sustainable management of Caspian energy resources requires a combined approach of joint agreements, active diplomacy, and strengthening domestic capacity.