Most individuals living with and beyond cancer are not sufficiently active to achieve the health benefits associated with regular physical activity (PA). The purpose of this study was to describe the study protocol for a two- arm non-randomised comparison trial conducted within a community-based setting, which aimed to investigate the clinical effectiveness of a cancer-specific PA behaviour change (BC) intervention, namely MedEx IMPACT (IMprove Physical Activity after Cancer Treatment), compared to a general exercise rehabilitation programme, among survivors of cancer. Individuals who had completed active-cancer treatment who were referred to a community-based exercise rehabilitation programme were invited to participate in the trial. Participants in the control group (CG) attended twice-weekly supervised exercise classes for 12 weeks. Classes were delivered as part of a chronic illness exercise rehabilitation programme. Participants in the MedEx IMPACT intervention group (IG) also attended the twice-weekly supervised exercise classes for 12 weeks and received cancer-specific materials, namely an independent PA programme, 4 PA information sessions and a 1:1 exercise consultation. The primary outcome was PA levels measured by 6-day accelerometry and self-report PA. Secondary outcomes included cardiorespiratory fitness (CRF), quality of life (QoL) and sedentary behaviour. Outcomes were measured at baseline and months 3, 6 and 12. Few effective PA BC interventions for individuals living with and beyond cancer have been identified. The results of this study will have implications for the planning and provision of community-based exercise oncology rehabilitation programmes for individuals living with and beyond cancer.