This research study seeks to explain the kind of behavioral logic that the European :union: has been following towards the Joint Comprehensive Plan of Action (JCPOA). In other words: What is the basis of the EU's attitude towards JCPOA? The hypothesis of the article, which has been developed descriptively-analytically, is that the EU foreign policy (behavior) towards JCPOA follows from the normative logic of the EU (good governance, democracy, human rights, rule of law, economic development, immigration regimes and Security regimes) with the aim of changing Iran's behavior. Therefore, the research findings indicate a deep-seated potential at the core of JCPOA, which plays a key role in the pattern of behavior of the European :union:; This means that the European :union:, on the one hand, takes action to create norms to solve international issues and, on the other hand, implements its foreign policy through these norms. From this perspective, the European union؛ views the JCPOA as a norm to change Iran's behavior and considers it as some kind of normative regime that includes the rules in order to regulate Iran's behavior in the nuclear field.