After the collapse of the USSR the legal status of the Caspian Sea remains unregulated. Nevertheless, the former Soviet republics and Iran carry out research and development of the resources on the territory of the Caspian Sea. The region's economic interests are very important (it is the main forming factor for political relations around the Caspian Sea). This research analyses the rules of international law interacting with each other regarding the Caspian Sea and the validity of the international agreements concluded by the Caspian states on the Caspian Sea. The conflictual influence of third-party including non-coastal states arising in this connection was also examined. The directions of the improvement of the international legal regulation of the matters connected with the use of the Caspian Sea were demonstrated. The author proposes the models how to regulate the dispute by means of the third party or addressing for its consideration into the international authority, as well as the concepts for the improvement of the regulation of the legal status of the Caspian Sea and increasing effectiveness of legal regulation on its use.