Background: Men with metastatic castrate-resistant prostate cancer can experience an array of treatment-related side effects. Accumulating evidence suggests exercise may alleviate some of these adversities and assist in disease management. However, empirical evidence in advanced prostate cancer patients remains limited. The purpose of this study is to determine whether men with metastatic prostate cancer, who are ineligible for high-intensity exercise, can partake in a home-based, moderate-intensity exercise program and the impact of doing so on quality of life and physical fitness parameters. Methods: Thirty men with adenocarcinoma of the prostate and progressive systemic, metastatic disease will be recruited. Clinicians will screen patients against inclusion criteria to determine eligibility. All men enrolled will be prescribed a tailored, home-based, moderate-intensity exercise intervention consisting of aerobic and strengthening components for 12 weeks. Patients will receive supplementary education materials and weekly behavioural change consultations throughout the intervention. The primary outcome will be the feasibility of delivering such an intervention in men with metastatic disease. Secondary endpoints including skeletal events will be monitored for safety, as will the feasibility of patient-reported outcome measures and the sampling time points, generating data pertaining to completion rates and potential effect in future trials. General physical fitness will be assessed during these visits, using timed sit-to-stand testing and a 6-min walking test. Prior to each visit, objective physical activity levels will be captured for 7 days using an accelerometer, to determine the feasibility of this technology and the quality of data obtained. In parallel with the feasibility aspects of the trial, changes compared to baseline will be reported. Direct regular contact will also serve as a feedback loop, should any issues arise. This study has received ethical approval from the Office for Research Ethics Committees Northern Ireland. Conclusions: This study aims to determine the potential utility of a home-based exercise intervention in managing side effects associated with advanced prostate cancer and its treatment. This feasibility trial will inform the design and implementation of a larger randomised control trial to determine the efficacy of moderate aerobic and strengthening exercise as an adjuvant therapy in men with metastatic prostate cancer. Collecting such evidence provides further support for exercise in this paradigm and potential for its inclusion as a low-toxicity therapy in standard cancer care, in the longer term.