Interdisciplinary study is a type of science which has become necessary after the shortcomings of specialization were found in science. Thus, we can say one reason that today the tendency is toward interdisciplinary, is specialization. Today mankind is facing complicated and multidimensional issues and consequently he needs multidimensional and interdisciplinary understanding and approaches to solve them. The goal of this article is to study the nature of knowledge and then to analyze the necessity of interdisciplinary studies in humanities according to Habermas’s point of view, a known representative of the Frankfurt School and Critical Theory. Using reliable texts and analytical methods, this study tries to answer to its main question, namely the nature of interdisciplinary approach in humanities. In the era ofmodernity, Habermas tries to show that the entirepart of humanmind abilitieshas been overcome by some of its part under the natural sciences and that it has prevented the recognition of the real world and created contrast between qualitative and quantitative methods in humanities. By criticizing the positivist approach and in the next step by proposing the theory of Communicative Action and Communicative Rationality, he emphasizes on the multidimensional nature of human knowledge and human issues and seeks to solve complex human issues through convergence and consensus on the ideal situation.