Since its inception in 1979, and its subsequent domination as a theoretical paradigm, Neorealism has become the target of wide criticism from a variety of approaches. The last and the most sever criticisms came from Constructivism. Constructivism rejects the rationalist methods and materialist assumptions of Neorealism, and aspires to introduce a sociological perspective for theorizing about the outcomes of international politics, and hence establishes itself as an alternative paradigm that provides more comprehensive explanations. It is, therefore; the purpose of this study to develop a comparative perspective for understanding the main concepts and issues of IR theory as they appear in the current debate in the field, and from within this debate to compare the two competing paradigms on four grounds. First, the study compares their conceptualizations of the Agent-Structure relation; how such conceptualizations affect their explanatory powers. Second, the study compares how the two schools understand and comceptualize “Anarchy” as a central concept in IR theory; and explores the theoretical effects of such understandings. Third, how the two schools understand the concept of identity and how do they employ it in their theoretical structures. Finally, as a result of their different understanding of the structure of international politics, how both schools perceive the possibility of change in International Relations.