An anterior urethral valve with diverticulum is an uncommon cause of congenital urethral obstruction and urinary extravasation compared with a posterior urethral valve. We report a neonate presenting with an abdominal wall urinoma caused by rupture of an anterior urethral diverticulum. Urine drainage via urethral catheter was effective to resolve the abdominal urinoma. Voiding cystourethrogram performed 6 months after an endoscopic incision of the distal margin of the diverticulum revealed a normal urethra with smooth voiding. To our knowledge, no similar case has been reported previously.