In an era of shifting global geopolitical, geostrategic and geo-economic power, ASEAN’s resilience as a regional grouping and its relative success in keeping internal conflicts at bay through various forms of quiet diplomacy and adherence to certain norms and binding principles mean that it may become a force helping to foster peaceful and stronger regional linkages within the eastern frontiers of the Indian Ocean Region (IOR). In this article we focus on ASEAN’s growing roles and relations within three key ‘spheres’ of adjoining regional-extra-regional reach, which we identify as the mostly landward Greater Mekong Sphere (GMS), the South China Sea Sphere and the Bay of Bengal and Andaman Sea Sphere. The Bay of Bengal and Andaman Sea straddle between the Indian Ocean Region and ASEAN, so this offers a joint issue of cooperation and proximate regionalism. As for the GMS and South China Sea, the common Chinese factor holds important geo-economic and geopolitical references that IOR could incorporate into its foreign policy portfolio. Despite ASEAN’s at times belowpar performances and contradictions in terms of regional and internal security, its direct and adjacent interconnectedness with the IOR suggests that it is perhaps one of the best institutions to learn from in terms of strengthening the IOR’s future regionalism aspirations.