The negotiation process of the Regional Comprehensive Economic Partnership (RCEP) has been challenging for its participating countries, who have sought to find a balanced compromise and consensus in spite of their many different interests. While some scholars have studied the RCEP negotiation, there has been no detailed study exploring how domestic interests influence leaders’ positions on the RCEP deal. The objective of this study is to explore the interests of major countries – China, India, and Japan – in the negotiation of the RCEP. China and Japan decided to stay within the RCEP formation, while India opted to stay out of the RCEP formation. This study argues that domestic interests have influenced leaders’ decisions in the RCEP negotiations. The existence of major countries shows hegemonic rivalry/game in the development of the RCEP. The neoliberal institutionalism theory has emphasised the importance of common interests for international cooperation. The existence of common interests has become a fundamental element for the conclusion of the RCEP to achieve its objective, namely economic integration, economic development, and strengthening economic cooperation.