The Trans-Caspian pipeline project is a controversial proposed oil and gas transportation initiative in the Caspian region that aims to bring energy resources from landlocked Central Asian republics, particularly Kazakhstan and Turkmenistan, to Europe, bypassing Russian territory. The project was postponed several times since early 1990s due to political, economic, environmental and legal reasons, the most prominent of which is the legal status issue of the Caspian basin. The Caspian is also known for its unique ecological system and endemic species, such as the sturgeon population. However, due to enhancing oil and gas development if the region and projects like Trans-Caspian pipeline, it faces challenges of environmental pollution and degradation. One of important mechanisms that could assist the Caspian littoral states to prevent further deterioration of environmental situation and minimize the possible transboundary impacts is the establishment of the harmonized national EIA procedures and procedure of transboundary EIA in the Caspian. This thesis explores the challenges of the transboundary EIA legislature in the Caspian Sea region by assessing the perspectives of proposed Trans-Caspian pipeline project through the prism of the existing issues of legal status of the Caspian basin and political rivalries. Despite general comparability of the national legislation on EIA in the Caspian littoral states, and already existing agreements on the need for procedures of transboundary EIA, the ongoing process of development has not yet reached the objectives of proper functioning legislative framework. The draft Protocol on transboundary EIA to Tehran Convention is based on the provisions of the Espoo Convention, though several difficulties of the legislature and its application were found. Deficiencies in the national EIA legislature, including lack of practice in transboundary EIAs, insufficient public participation and formality in its application, the lack of importance given to environmental issues in the strategic decision making process found to be the most important issues that should be considered in the evaluation of the possibility of construction of cross border projects, in this case Trans-Caspian pipeline project.