This article sets out what would be required to develop a research agenda for impact evaluation. It begins by explaining why it is needed and what process it would involve. It outlines four areas where research is needed – the enabling environment, practice, products and impacts. It reviews the different research methods that can be used to research impact evaluation and argues for particular attention to detailed, theory‐informed, mixed‐method comparative case studies of the actual processes and impacts of impact evaluation. It explores some examples of research questions that would be valuable to focus on and how they might be addressed. Finally, it makes some suggestions about the process that is needed to create a formal and collaborative research agenda.