The Caspian Sea region is of high importance regarding energy related geopolitics, energy transporting lines and security within regional and international relation. After the fragmentation of USSR and the increase of number of the Caspian coastal countries from two to five, the issue of determining a legal resolution for the Caspian Sea became more complicated. Thus, the regional and trans-regional countries benefits and maximize their power within the international system in the region among which the encounter between America and Iran is the most salient. In this paper it has been tried to explain this problem in the region employing the analytical – descriptive technique based on theoretical approaches of energy – related geopolitics. In this direction, findings indicate that the conflicting policy of the two countries, America's attempt to eliminate the geopolitical situation of Iran from transportation of energy in the region, the effectiveness of America on debates relative to determining a legal resolution on the Caspian region by resorting to military and security solution and threatening Iran's interests and national security are among the most important reasons for this encounter. Finally the Islamic Republic of Iran can obtain its main interests within the legal resolution for Caspian Sea and find its place as the connecting chain among producers and consumers of energy, by a correct understanding of its geopolitical capabilities within foreign policy and active and smart diplomacy. In fact, it is the best way to achieve the economic development, as well as to tie the international economy to its national security and to minimize the relative threats.