Environmental policy integration (EPI) refers to the incorporation of environmental concerns in non‐environmental policy sectors. EPI aims to avoid conflicts between environmental and other policy objectives and to enhance environmental policy by directly targeting the driving forces of environmental degradation. In practice, however, the potential of EPI has not been fully utilized. Scientific knowledge of EPI is found in several, largely isolated, bodies of literature (on EPI, climate policy integration and environmental impact assessment/strategic environmental assessment) and does not provide an adequate answer to the question of what EPI strategies work, where and why. A systematic framework based on comparative empirical research is required to contribute to more effective EPI strategies. In this paper we formulate a research agenda for the development of such a framework on the governance of EPI that is robust, i.e. builds on other theories of environmental governance and policy change and that envisages large‐scale, international comparative empirical analysis. Copyright © 2014 John Wiley & Sons, Ltd and ERP Environment