In its contemporary history, Iran has experienced three different politi-cal systems, each of which, the Qajar, Pahlavi and the Islamic Republic, has had different foreign policies. There are many instances of Iran's foreign policy during this period such as acting as a buffer state, efforts made to employ a third force, a policy for nationalizing the oil industry, a strategic alliance with the United States, the neither East nor West policy, and attempts to change regional landscape, which may seem contradictory and sometimes irreconcilable. To give an account for this apparent contradiction, this paper seeks to revisit Iran's foreign policy during these three political systems in order to propose a general theo-retical model which, we argue, the literature on Iran's foreign policy lacks. To do this, we go through three different sections: First, based on a historical sociological perspective, the necessary and adequate factors are considered to create an analytical and comprehensive model. Second, a theoretical model of Iran's foreign policy is pro-posed based on state-society relations. Finally, to demonstrate the analytical capability of this model and its link to Iran's foreign policy history, a brief account of Iran's foreign behaviors in contemporary history will be presented.