Critical policy analysts aim to serve policy actors in dealing with the intricate problems they face by facilitating productive communication, critical learning and sustainable change. Action research is a valuable approach for living up to this ambition. As it is rarely used in the field of critical policy analysis, this symposium further explores what action research has to offer. In this introduction, we draw out the main principles, practices and dilemmas of action research, provide an overview of the four contributions to the symposium and set out an agenda for future action research. We argue that action research is a useful approach for generating reflexivity, learning and change among the actors implicated in the problem at hand and its wider context, as well as for grasping the meaning of ‘knowledge’ and ‘research’ within current science-practice relations. At the same time, it is challenging because, in practice, it means facing the diverse, contested meanings of usable knowledge in both of these settings. Hence, we encourage future action research to further come to terms with the actual possibilities and constraints of the transformative ambitions of CPS.