Background <p>Manual wheelchair (MWC) training is evidenced as a crucial intervention provided to many populations, however gaps in provision occur for individuals commencing wheelchair use in later life due to chronic and progressive conditions. Effective training can improve independence and engagement in meaningful activities and reduce injury risk, caregiver burden and reliance upon healthcare services. However, not all training contexts yield positive outcomes for all MWC users. Using a realist approach, this study describes the development of middle range theories to provide insight into the contexts and mechanisms that underpin successful manual wheelchair training outcomes.</p> Method <p>A realist approach synthesised evidence from primary studies (<i>n</i> = 47) and stakeholder interviews (<i>n</i> = 17) to explore the contexts, mechanisms and outcomes underlying manual wheelchair training effectiveness. Retroductive analysis was used to build and refine initial programme theories to explain why and under what circumstances a MWC training intervention may be working. To enhance explanatory power, we considered existing rehabilitation and learning theories, leading to the development of middle range theories that offer generalisable causal explanations of how and why MWC training works.</p> Results <p>Five Middle-Range Theories (MRTs) were developed. MRT 1: Resources and structured guidance enhances user confidence; MRT 2: The delivery of person-centred, goal-directed training enhances motivation, user acceptance and engagement in MWC training; MRT 3: Training in safe and relevant environments facilitates MWC user confidence and willingness to engage in training. MRT4; Training in environments with positive social attitudes towards wheelchair use enhances psychological safety and acceptance of wheelchair use. MRT 5; Including peers, peer trainers and care partners in MWC training is motivational and supports self-efficacy in wheelchair use. Collectively these MRTs reflect the importance of a well -resourced, user-centred, socially supportive and contextually relevant approach to MWC training.</p> Discussion/Implications <p>This research highlights the need for system-wide reform to improve MWC training for individuals with chronic and progressive conditions. Key priorities include addressing funding disparities, integrating services across sectors, delivering training in authentic, inclusive environments, providing flexible, person-centred approaches, building workforce capacity and embedding accountability into MWC training.</p>