In this article, we present a psychosocial theory of partnership, illustrated with case studies from Cambodia and Brazil. Partnerships are conceptualised as encounters with the knowledge of self and others, entailing processes of representation and communication between all stakeholders involved, and shaped by institutional and sociocultural contexts. We argue that partnership is an evolving practice that requires critical reflection and the creation of enabling institutional contexts. As such, it must be understood not as a tool for intervention, but as part of the intervention and definition of success.