This article explores the complex ways in which development NGOs become professional development actors. It offers a uniquely holistic understanding of professionalisation that draws on extensive new research data. It challenges the accepted narrative, presented by development scholars, of neoliberalism as the fundamental driver of professionalisation. Instead, it offers a more nuanced theorisation that recognises that professionalisation from outside, driven by neoliberalism, is often preceded by a professionalisation from within. Here the paper develops the concept of self-legitimising professionalisation as part of a ‘two stage process’ through a case study of international development practice delivered by UK based development education actors.