A 25-year-old woman had a urethrovaginal fistula caused by a foreign body in her vagina. The patient had sought an appointment with a gynecologist for removal of the foreign body in her vagina. However, one day before the scheduled appointment, she developed acute urinary retention and visited the emergency room of our hospital. A urinary catheter inserted into the urethra was found to come out through the vagina. The foreign body, a bottle cap made of polypropylene and measuring 48 x 28 mm in size, was removed. A cystourethroscopic examination confirmed the presence of the urethrovaginal fistula. Repeat cystourethroscopy performed after one month of conservative management showed a persistent urethrovaginal fistula, which had, in fact, increased in size as compared with that at the initial examination. Surgery was undertaken for repair of the fistula ; fistula closure was successfully accomplished by suture in three layers : urethral wall, subcutaneous tissue, and the vaginal wall. This is the second report of a urethrovaginal fistula caused by a foreign body in the vagina.