Decades of increase in external aid programs sparked a wide range of criticisms pointing to misaligned interests, lack of accountability, and the reproduction of developmental traps. The success of development from without is more likely if it generates domestic developmental agency. In this article, we contribute by conceptualizing and measuring dimensions of developmental agency. Our research analyzes the strategic case of European Union regional development programs in Eastern Europe, where this external organization spent nearly a decade on establishing local developmental agency. We collected survey data of 1.200 local organizations from two regions in each of Czech Republic, Hungary and Poland. We examine the post-accession position of organizations that participated in pre-accession assistance programs. We test a hypothesis of marginalization in the framework of recentralized developmental governance, and we examine links between patterns of pre-accession involvement and post-accession developmental agency. We identify factors that might make external developmental programs more likely to foster local developmental agency.