yes / Background: Experience-Based Co-Design (EBCD) is a participatory design method which was originally developed and is still primarily used as a healthcare quality improvement tool. Traditionally, EBCD has been sited within single services or settings and has yielded improvements grounded in the experiences of those delivering and receiving care. Method: In this article we present how EBCD can be adapted to develop complex interventions, underpinned by theory, to be tested more widely within the healthcare system as part of a multi-phase, multi-site research study. We begin with an outline of co-design and the stages of EBCD. We then provide an overview of how EBCD can be assimilated into an intervention development and evaluation study, giving examples of the adaptations and research tools and methods that can be deployed. We also suggest how to appraise the resulting intervention so it is realistic and tractable in multiple sites. We describe how EBCD can be combined with different behaviour change theories and methods for intervention development and finally, we make suggestions about the skills needed for successful intervention development using EBCD. Conclusion: EBCD has been recognised as being a collaborative approach to improving healthcare services that puts patients and healthcare staff at the heart of initiatives and potential changes. We have demonstrated how EBCD can be integrated into a research project and how existing research approaches can be assimilated into EBCD stages. We have also suggested where behaviour change theories can be used to better understand intervention change mechanisms.