Renal transplant recipients are a population usually considered at a higher risk of malignancies, mostly skin cancer and lymphoproliferative disorder. In recent years, prostate cancer in renal transplant recipients has been becoming more frequent. This is probably due to the growing age and the longer survival of the transplanted patients. We report the case of a 50-year-old man with prostate cancer and renal allograft, who received radiotherapy after prostatectomy at the Institute of Radiotherapy of the University of Florence. Radiotherapy is part of the standard treatment for many cases of prostate cancer. According to the few series reported in the literature and also to our experience, radiation therapy is feasible also in renal transplant recipients with accurate treatment planning.