Climate change is an issue that cuts across several policy domains, from the environment to transport, industry, agriculture, and health, among others. It follows that responses to climate change need to cut across the various policy fields also. The phenomenon of incorporating or mainstreaming climate policy into other policy fields is often termed “climate policy integration”, and it is a policy requirement that has not yet been extensively explored, especially at EU level. With the agreement on the EU’s integrated climate and energy package in December 2008, it is clear that climate policy integration is considered important for the Union’s strategy to combat climate change. Can it be said that climate policy integration is already in place in the EU? How can we identify climate policy integration? How can we ensure that climate policy integration is effective? The aim of this paper is to examine the extensive research already carried out on environmental policy integration (EPI) in order to draw out lessons that could help, firstly, to conceptualize climate policy integration, and, secondly, to identify a framework for analysis or a set of criteria that could aid the analysis of climate policy integration at EU level. EPI is an area of literature that rarely deals with climate policy in particular. However, its focus on policy processes, administrative structures and communication channels, for example, can provide lessons for the study and implementation of climate policy integration. This paper contributes to the development of an analytical framework for assessing and studying climate policy integration at EU level, and concludes by highlighting some areas for further research.