Retroperitoneoscopic partial cystectomy was performed to remove a leiomyoma in the right wall of the bladder in a 58-year-old man. The tumor was initially circumscribed with a mucosal incision using a transurethral resectoscope, and once the bladder wall had been penetrated with the resectoscope, the remaining procedures were performed retroperitoneoscopically. The bladder wall was closed using a retroperitoneoscopic suturing technique. Endoscopic partial cystectomy using both a transurethral incision and a retroperitoneoscopic resection is technically feasible in the treatment of small bladder tumors.