It is not rare anymore to find patients with knowledge and experience of a care pathway integrating a team of health professionals in order to improve the quality and relevance of their peers’ care pathways. The aim of this article is to propose practical methodological answers and structuring questions to institutions and any health actor interested in integrating a Patient Partner (PP) into a team of health professionals. The results of an action-research (AR) carried out within a Cancer Treatment Centre (CTC) provide both a methodological framework and answers to the questions raised by this experimentation: How did the team and the PP organize themselves to implement the mission of peer support? What evaluations of the project should be put in place? How does everyone find their place in the project? And finally, what are the operational procedures, limits, and levers for integrating the PP into the team? In the discussion section, we propose a model of experimentation based on AR, highlighting the main drivers and the interventions that feed them. Finally, we share a series of structuring questions arising from the co-construction work carried out by the people involved, which allowed us to build our action plan for the integration of a PP in the care team at the Rennes CTC, and which seems to us sufficiently generalizable to be tested and used by other teams and in other contexts.