An endolymphatic sac tumor (ELST) is a tumor of neuroectodermal origin. Although several cases have been reported in Korea, it is known to be very rare. Clinically, it grows slowly but shows an aggressive pattern accompanied by bone destruction pathologically. As the tumor grows, it shows symptoms due to endolymphatic hydrops such as hearing loss, tinnitus, and dizziness. In this paper, we report a case in which an ELST was found in a patient suffering from profound sensorineural hearing loss, tinnitus, and dizziness, who turned out to be an enlarged vestibular aqueduct syn-drome.