The following case is about a 25-year-old female patient. On the physical examination, it was found that she had a submental mass and, in the observation of the oral cavity, it was possible to observe that the same mass caused a postero-superior displacement of the tongue. In the observation of CT scan, it was possible to identify a large delimited lesion that caused a narrowing of the airways, causing dysphonia, dysphagia and dyspnea. The excision of the lesion was performed with sublingual access. After histological analysis the lesion was diagnosed as being a dermoid cyst. Dermoid cysts in the mouth appear as slow-growing masses, often located in the midline of the floor of the oral cavity, and are caused by retention of the germinal epithelium during the growth of the branchial arteries of the mandible and hyoid in a failure of the embryonic closure. These lesions are considered to be rare in the head and neck region with an incidence of 1.6 to 6.9% and represent less than 0.01% of all cysts in the oral cavity. This is a case of an unusual pathology since this is a cyst that appears infrequently in the oral cavity and in this case also the dimensions of the lesion are rare. This was a case of success since the enucleation of the lesion was performed by the floor of the oral cavity, which allowed an improvement in the quality of life of the patient, and there was no aesthetic or functional impairment. Keywords: dermoid cyst