Iran nuclear negotiations, which resulted in an agreement in Vienna on the 14 July 2015 after signing The Joint Comprehensive Plan of Action, and its aftermath is one of the key topics of inquiry in recent decade. The density of the debate is primarily emanating from concerns related to the security questions of the Middle East and to the sensitivity of Israeli security situation. Moreover, it arises from the complexity of the whole negotiation process. Such issues like Supreme Leader’s Ali Khamene’i’s fatwa designating sinfulness to the nuclear capacity, his after-deal speech, calling for the enmity between Iran and the United States, Iran’s declared aim to implement global justice and other cases are not customary acts of the state and the study of Iranian foreign policy is not substantive using customary instruments of analysis of International Relations. The article refers to the problem of knowledge production on Iran, and suggests that it mainly resulted from the lack of exchange between International Relations and Middle Eastern studies. This article aims to point at the authority of the ideas in Iran’s foreign policy that Islam or Islamic ideologies like Khumaynism produce. Therefore the article focuses on the main narratives of the First Supreme Leader Ruhullah Khumayni’s concept of justice in order to, first, explain the key points in Iran’s position during negotiations and its aftermath and, second, to introduce the study of the concept of justice as a productive source of information and an approach for further analysis of Iranian foreign policy.