This paper presents an assessment of the Tehran Convention’s influence on environmental data-sharing practices in the Caspian Sea region. The Caspian Sea, a distinct ecological system shared by Azerbaijan, Iran, Kazakhstan, Russia, and Turkmenistan, faces environmental challenges such as pollution, biodiversity loss, and climate change impacts. Through a multi-method approach, combining document analysis and qualitative interviews with key stakeholders, the study investigates the dynamics, determinants, and implications of data sharing for regional cooperation. The Caspian Environmental Information Center (CEIC), an online platform established by the Tehran Convention to facilitate information exchange, serves as a case study to analyze the factors shaping data-sharing practices. The sociology of technology is applied to explore the role of technical infrastructure and platforms in mediating data exchange, while the sociology of information sheds light on the management and dissemination of environmental data. Findings reveal that CEIC’s effectiveness is shaped by a complex interplay of technical, political, and social factors, including disparities in technological capacity among littoral states and political tensions. Despite these challenges, the CEIC’s flexible and consensus-driven approach has proven instrumental in fostering collaboration and identifying pathways for improving data-sharing mechanisms in a controversial geopolitical landscape. The paper concludes by advocating alternative data-sharing strategies that prioritize trust-building and incremental progress toward cooperative governance. It highlights the need to adapt data-sharing frameworks to the specific geopolitical and environmental contexts of transboundary regions, challenging traditional models that prioritize open access to raw data.