Whilst the role of trust between the states constituting the Association of South East Asian Nations (ASEAN) has been recognised, there have been few studies that focus on the concept and the dynamics of this trust. This is problematic, as scholarship surrounding ASEAN is engaged in a debate on whether, and the extent to which, the regional organisation constitutes a Security Community – a concept in which trust is recognised as playing an important role, even if trust is again under-conceptualised. This chapter addresses this omission through a case study of ASEAN’s creation in 1967. By analysing the creation of ASEAN, the chapter demonstrates that rational trust is indeed a useful beginning point when analysing the creation of organisations, despite criticisms of the concept.