Abstract: This article first conceptualizes the ASEAN Investment Regime (AIR) as an Interstate Cooperative Regime (ICR), defined as a stable interstate cooperative nexus on a particular regulative subject, comprising the regulation of foreign investment in this case. It then seeks to explain the evolution of AIR in terms of its identity formation. In doing so, this article employs three ideal types of cultural logic – Hobbesian, Lockean and Kantian – across each stage of AIR’s evolution, largely overlapping with the three main IR theories of neorealism, neoliberal institutionalism and constructivism, respectively. Using those models, we find a clear evolutionary pathway with the AIR following this sequential trajectory as it has transitioned towards a closer, regional investment community. This article nonetheless concludes that AIR’s organizational development has not always been linear and that one can detect sovereigntist regressionism in certain areas.