This research is going to examen the US policies toward Iran and its implications on regional security in the Persian Gulf during the period from 1979 – 2008. In addition, the study also evaluated the U.S. policies toward Iran in relations to the Persian Gulf during the presidencies of Carter, Reagan, George HW Bush, Clinton, and George Bush during this period of time. The objectives of the research were achieved by seeking answers to the two research questions: 1) What were the evolutions of the U.S. regional security policies regarding Iran in the Persian Gulf from 1979 to 2008?; 2) What were the influences of the U.S. regional security policies on the regional peace and stability regarding Iran in the Persian Gulf? according to the “Regional Security Complex Theory”, there were significant relationships between the rivalries of the regional states in the Persian Gulf and external interventions. The results revealed that local rivalries led to the interference by external powers in the region. In the case of Iran, the rivalries inside the Gulf Cooperation Council states and between them and Iran and Iraq led to U.S. intervention in the region.