Islamic Republic of Iran has faced many legal challenges over its nuclear activities for more than twelve years with some world’s major powers, the International Atomic Energy Agency (IAEA) and the United Nations Security Council. Islamic Republic of Iran and the 5 + 1 after several years of negotiations to resolve issues related to the Iranian nuclear program and sanctions against Iran, in July 2015 the text of a Joint Comprehensive Program of Action (JCPOA) was concluded and then shortly after that, according to what was agreed between the parties, the United Nations Security Council Resolution 2231 was adopted in this regard. The JCPOA is an international instrument that after several months of intensive negotiations on the Iranian nuclear issue was agreed in Vienna, Austria to terminate several year disputes between Iran and these countries. The JCPOA actually guarantee the peaceful nature of Iran's nuclear program and a fundamental change in the attitude of Europe and the 5 + 1 regard to this issue. Determining the nature of the JCPOA, both in terms of how its entry into force and the effects which its leaves, is very important.According to the 1969 Vienna Convention on the Law of Treaties if the JCPOA, is an international treaty no matter what name it is, Must comply with Article 77 of the Islamic Republic of Iran's constitution, approved by the Iran’s parliament and after approval by Parliament in accordance with Article 125 of Iran’s constitution to be signed by the President. But if theJCPOA is a political agreement, the commitment of the governments of the countries concerned is sufficient. In this paper, by investigating of the JCPOA position in the legal systems of Iran and America we show the place of this international document in these two countries.