Congenital immature teratoma of the tongue is a exceedingly rare form of epignathus. We report here an autopsy case of a huge immature teratoma protruding from the tongue of a newborn female infant. The mass obstructed the mouth and caused hydramnios. The mother's serum level of alpha-fetoprotein was elevated, and the tumor was identified by a ultrasonogram subsequently done. Discussion on the histogenesis of epignathus was made through a review of literatures.