<h4>Introduction</h4>Robot-assisted radical cystectomy for bladder cancer that develops after curative treatment for prostate cancer has not yet been reported.<h4>Case presentation</h4>A 65-year-old man underwent radical prostatectomy and received salvage radiotherapy after his postoperative prostate-specific antigen level failed to decrease. The gene discussed is KLK3; the disease is prostate carcinoma.