Claims about the decline of regionalism in world politics have overlooked the continuing development and expansion of Chinese initiatives. This article critically examines the conventional conception of regionalism and develops a new flexible conceptual approach to the form of Chinese led-regionalism, and in particular its state-centric variant. The article examines the roles of China-led regionalism in the context of US–China rivalry through the case studies of ASEAN plus 1 (China) regarding the South China Sea, and the Shanghai Cooperation Organisation. The article also brings two separate sets of literatures on the politics of alliances and regionalism together by examining the role of regionalism in modifying the logic of alliances. It finds that China-led regionalism has modified the logic of alliance politics by developing a hybrid and overlapping membership arrangement that blurs friend–enemy assumptions. China-led regionalism in the area of security, however, has not provided a mechanism that can manage the rivalry between the US and China due to its exclusive nature.