Recognising the limited literature detailing the practical application of co-production principles and practices within sport, exercise and health research, critical reflections on co-production principles and practice are shared here, drawing on two participatory action research (PAR) projects in the United Kingdom (UK). Co-production and PAR are distinguished, and their commonalities discussed. Both projects were facilitated by occupational therapists and concerned with health inequities and social justice. The Voices for Inclusive Activity project brought disabled people together online to explore more accessible and inclusive approaches to evaluate disability sport and physical activity. The Positive Mental Attitude project took place with a community-based football league for people with experience of mental distress and explored the nature and value of participation. Both projects involved researching with people who are often excluded from research. Addressing power imbalances can function to engage marginalised people in processes of knowledge production and enable social justice. Co-production offers useful principles that are democratic, inclusive, collaborative, and participatory, but the process is not straightforward. The reflections within this paper focus on the challenges and opportunities the first and second authors faced as facilitators of co-produced research. Participant and co-researcher quotes reveal how participatory methods and approaches address gaps in experiential knowledge of exclusion and marginalisation. The potential for co-produced research to influence policy and practice is outlined.