Rectourethral fistulas are uncommon and can be classified as congenital or acquired. We present a case of rectourethral fistula following a shotgun injury and describe a surgical method of closing poorly healing defects between the urethra and rectum by means of a muscular flap of the gracilis muscle (GM). A 20-year-old man underwent laparotomy and colostomy for gunshot trauma. In postoperative first week, the patient began complaining of urine coming from the rectum. Retrograde urethrography revealed a fistulous opening connecting the prostatic urethra and the rectum. The transperineal approach with a GM flap interposition is currently the most commonly used method and one of the effective procedures for treating complex fistulae. Morbidity after a GM flap interposition is known to be low. GM transposition is a useful and effective method for the treatment of rectourethral fistula.