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This article tries to answer the question that which realist theory can provide a more comprehensive and more appropriate conceptual framework for explaining the foreign policy of countries. Along these lines, the author, while mentioning the common foundations of realist views and their internal debates, describes how classical realism, structural realism, and neo-classical realism look to the notion of foreign policy. The emphasis of classical realism on the power – seeking nature of the man, the characteristics of states, and its insufficient attention to systemic factors, on the one hand, and the lack of attention of structural realism to the factors of unit level and its mere emphasis on systemic grand variables, on the other hand, are among the deficiencies of these two theories for explaining foreign policy. A more important point is that in neo-realism, the main dependent variable the theorists are to explain, is international implications of an event or a phenomenon, and studying foreign policy does not constitute their main preoccupation, while neo-classical realism posits foreign policy as its dependent variable. This theory, in the first instance, is a theory for explaining the foreign policy of the states. The main argument of this article is that neo-classical realism can provide a more comprehensive conceptual framework for explaining foreign policy compared to classical and structural realism because of its simultaneous attention to system level factors as intermediate variable, and also positing foreign policy as the main dependent variable;
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