Dermoid cysts are for the most part benign neoformations most likely deriving from ectodermic differentiation of totipotent cells. Although localization on the floor of the mouth has been described for more than a century it is still reported as rare and can give rise to problems in differential diagnosis. This work presents a case of dermoid cyst of the floor of the mouth in a 16-year-old patient and provides considerations on clinical approach, diagnosis and therapy for this type of lesion.