Background Despite the proven benefits of exercise rehabilitation for numerous health conditions, musculoskeletal injuries and recovery from surgery, patient adherence to such programs is reported to often be less than 35%. Increasing patient engagement therefore has the potential to improve patient health outcomes, benefiting the patient, their carers and the services that support them. The aims of this review were to identify the factors that contribute to ‘patient’ engagement in prescribed exercise rehabilitation using the COM-B (Capability, Opportunity, Motivation – Behaviour) framework of behavioural analysis. Methods Five electronic databases (PubMed, Embase, Cochrane, Web of Science, and ClinicalTrials.gov) were searched. ‘COM-B’ was the key word searched for specifically within titles and abstracts, combined with either ‘physical activity’ OR ‘exercise’ included using the ‘AND’ operation. Records were then filtered and excluded following full-text screening based on the predetermined eligibility criteria. Results Twenty studies were included in the review. The main COM-B themes highlighted for improving patient engagement were: Capability - improving patient knowledge and cognitive skills for behavioural regulation, such as ‘Action Planning’ and ‘Action Control’, which could also benefit time-management; Opportunity - a balanced life situation that enabled time to be devoted to the exercise program, social support, easily accessible and affordable resources and services; and Motivation - increasing patient levels of self-efficacy and autonomous motivation, which were noted to be influenced by levels of perceived ‘Capability’, additionally ‘Motivation’ was noted to be influenced by patients perceiving the benefits of the exercise, and adherence to the program was promoted by ‘goal-setting’. Other issues in the ‘Capability’ domain included a fear and/or dislike of exercise. Conclusion Patient engagement behavior has been shown to be influenced by both external (Opportunity) and intrapersonal variables (Capability and Motivation). Those prescribing exercises within a rehabilitation program need to discuss these factors with their patients and co-design the exercise rehabilitation program in partnership with the patient, since this is likely to improve patient engagement, and thereby result in superior health outcomes. Furthermore, these factors need to be a consideration in clinical trials, if the findings from such trials are to translate into mainstream healthcare settings.