The purpose of this research was to identify the law applicable to the delimitation of the Caspian Sea and selecting the best approach in this regards. In this sense, in the beginning, the geopolitical significance of the Caspian Sea in the region and the importance of the Convention on the Legal Status of the Caspian Sea were reviewed. In order to examine applicable law, international legal resources under Article 38 of statute of international court of justice (ICJ) and the best current approaches, standards, principles and methods for international maritime delimitation were discussed. Furthermore, the main source of current and past legal statutes of the Caspian Sea, Soviet-Iranian agreement, bilateral agreement on the northern part of the Caspian Sea delimitation and the Caspian Sea Convention was considered. In addition, special conditions and circumstance of the Caspian Sea coast were assessed, and the best approach for the demarcation of the Caspian Sea, the three stage approach, was analyzed. It is worthy to mention, this work is a compressed and update version of my Master thesis1 at world maritime university.