Over the last decade, a new developmentalism has taken root across Africa, centred on promoting local production and industrialisation. One unintended consequence of this has been the proliferation of economically nationalist policy measures that have increasingly come into tension with the aims of regional integration in Africa. This article sets out to offer insights as to why these tensions are emerging by focusing on the East African Community (EAC) and the growing trend of economic nationalism among its members. Contrary to what rationalist and structuralist accounts might presume, this article argues that this rise in economic nationalism is instead reflective of a weakening of the discursive imperative – or social purpose – that had initially converged various actors around the EAC's integration agenda when revived in 2000. While drawing from the EAC's experience, it concludes by highlighting a broader legitimacy dilemma facing African regional organisations within this ‘new developmentalism’.