This chapter examines the Eurasian Economic Union (EAEU) from the perspective of the main theories in the Discipline of International Relations (IR). The author sketches out the main stages of the development of the EAEU cooperation by highlighting the conceptualization of the scheme by President Nazarbayev of Kazakhstan in 1994, the establishment of the Customs Union (CU), and the Common Economic Space (CES) between Russia, Belarus, and Kazakhstan in 2010. Theories analyzed include Neo-Realism, Neo-Classic Realism, Hegemonic Stability Theory, Liberalism, Functionalism, Neo-Functionalism, Neo-Institutionalism, the English School, Constructivism, and Neo-Gramscian Theory. The author makes an overall evaluation and stresses the need for an eclectic approach for analyzing the EAEU experience.