This dissertation deals with post-Cold War interdisciplinary debate between International Relations and International Law. Having considered that some conventional conceptions held in the field of International Relations are responsible for misunderstandings in respect with the relation of this discipline and International Law, we are first concerned with the historical perspective. Then, we focus post-Cold War interdisciplinary debate through the lenses of three distinct theories, Institutionalism, Liberalism and Constructivism. Finally, we argue that Constructivism is more able to develop a deeper cooperation between International Relations and International law. This is due to the connections between Constructivism and Critical Theory.