Abstract Background Previous systematic reviews and meta-analyses demonstrated beneficial effects of exercise during or following cancer treatment on quality of life (QoL). Aiming to understand how exercise contributes to a patient's QoL, we examined patients' perspectives via a process called concept mapping. This unique method provides structure and objectivity to rich qualitative data. Methods Patients with cancer who were participating in an exercise program were invited to enroll. Eleven meetings with 3–10 patients were organized in which patients generated ideas in response to the question “How has participating in a supervised exercise program contributed positively to your QoL?” Next, patients individually clustered (based on similarity) and rated (based on importance) the ideas online. The online assessments were combined, and one concept map was created, visualizing clusters of ideas of how patients perceive that participating in a supervised exercise program improved their QoL. The research team labelled the clusters of ideas, and physiotherapists reflected on the clusters during semistructured interviews. Results Sixty patients attended the meetings; of these, one patient was not able to generate an idea in response to the statement. Forty-four patients completed the online clustering and rating of ideas. The resulting concept map yielded six clusters: personalized care, coaching by a physiotherapist, social environment, self-concept, coping, and physical fitness and health. Personalized care was rated as most important. Overall, physiotherapists recognized these clusters in practice. Conclusion Patients with cancer reported that participating in a supervised exercise program improved their physical fitness and influenced social, mental, and cognitive factors, resulting in improvements in QoL. These results can be used to increase the awareness of the importance of supervised exercise programs for the QoL of patients with cancer.