The article examines the compatibility of nationalist ideology and regional integration within the European Union (EU) and the Association of South-East Asian Nations (ASEAN). In exploring nationalist ideology as a third alternative to functional and identity-based approaches to regional integration, it contributes to debates on the necessity and desirability of a common supranational identity. Despite a hitherto largely transaction-based approach to integration, political elites in South-East Asia have expressed support for ‘ASEAN awareness’ or ‘cognitive regionalism’ in the hope of increasing the organisation’s social cohesion and solidarity. These constructs seek to supplement political and economic co-operation with a sense of imagined (regional) community, despite the lack of strong supranational institutions within ASEAN. Their aim is thus to replicate a quasi-national construct at the regional level, something which has met with relatively little resonance within EU member states. The similarities between government attempts to foster a sense of regional belonging and nation-building principles, let alone their interplay, have yet to be fully explored in the South-East Asian context. The article tackles the question of whether EU and ASEAN member states can learn from each other in developing approaches to regionalisation.