Once International Relations claimed a monopoly over the study of world affairs, there is now a plurality of capable observers from disciplines like Geography, International Political Economy, and Sociology. The role of diplomats in International Relations has two essentials: Decision making in political affairs, and judgment on ethical affairs. A diplomat does judgment on other diplomats, states, peoples, their words, and beliefs.The concept of national interest refers to welfare goals of national governments on the international level such as the preservation of political independence and territorial integrity.The term rational denotes behavior that is appropriate to specified goals in the context of given situation. A course of action can be qualified as rational or not only with reference to the actor’s own intrinsic rational preferences.To assess the rationality of statesman’s foreign policy we must determine whether he correctly weighs the national interests in a particular situation and chooses a policy or an option that is most likely to achieve the national interests at acceptable cost and risk.Having examined the doctrine of Thomas Hobbes about the man, it is impossible not to pay attention to one essential question. It is a question of what is the human nature in reality, what are desires and inclinations which define ultimately the people’s behavior. The answer of Hobbes is mostly clear and unequivocal: From birth people are exposed to greed, fear, anger and to other animal passions, they look for respect and profits; they act for the sake of benefit and fame, that is, for the love to themselves and not to others. Thus, egoism turns up to be the main stimulus of the human actions.National Interests, Rationality and Morality are three sides of a triangle which has interactions to each others. We discuss interactions and impacts of the triangle sides briefly. Iran as an ancient state with similar and different national interests during history, rationality in its decision making and ethical values at foreign policy can propose new paradigms of dialogue of international relations and morality.