Introduction Obese patients with coronary artery disease (CAD) or atrial fibrillation (AF) currently participate in regular cardiac rehabilitation (CR) programs. However, effects of CR appear smaller than in non-obese patients, and are rarely sustained over time. Purpose We study the clinical- and cost-effectiveness of a new patient-oriented cardiac rehabilitation program, OPTICARE XL, especially developed for obese CAD and AF patients. Methods In this multicentre randomised controlled trial, 200 cardiac patients will be included. Participants will be randomized 1:1 to regular CR or an intervention group. In the first three months patients in the intervention group receive 20-24 exercise sessions in a group with other obese cardiac patients. In addition, they receive 12 interactive group sessions about healthy weight and four sessions about active lifestyle management. Furthermore, patients can participate in regular CR sessions such as psychosocial therapy and stress management. Between three months and one year, the intervention group receives an aftercare program comprising six follow-up meetings, and access to a mobile chat with a dietician, physical therapist and other participants. The control group receives regular CR for three months. The main endpoints are health-related quality of life and cost-effectiveness, secondary endpoints are physical fitness, body composition, other cardiac risk factors and physical activity levels, assessed at baseline, three months, nine months (control group), 12 months (intervention group) and 18 months after inclusion. Initiator in this study is Capri Cardiac Rehabilitation Rotterdam. This work received funding from the Dutch Organisation for Health Research and Development (ZonMw, Grant number 843001702). Results The first results are expected in 2019. Conclusion This study will provide insight in (cost-)effectiveness of a novel cardiac rehabilitation program for obese patients with coronary artery disease or atrial fibrillation. We expect that a tailored program for obese cardiac patients results in improved outcomes compared to regular CR.