This guide is a resource document for the training and capacity building of facilitators who conduct participatory action research (PAR) in the CGIAR Research Program on Aquatic Agricultural Systems (AAS). AAS aims to improve the lives of poor and vulnerable people reliant on aquatic and agricultural systems for their livelihoods, through collaborative, inclusive PAR with communities and other stakeholders. This guide provides a road map for facilitators to support them in delivering a rigorous PAR process, providing them with guidance for effective facilitation that allows for critical reflection throughout the engagement process. It has been written with an explicit focus on the Tonle Sap hub in Cambodia. The material in the guide is also relevant to other AAS hubs.