Ascher syndrome is characterized by double lip, blepharochalasis, and non-toxic goiter triad. This condition of unknown etiology usually occurs in patients younger than 20 years of age. In this case report, the authors present the diagnostic process of Ascher syndrome and surgical procedure of double lower lip in a female patient who applied to our clinic for prosthetic reasons. A 70-year old female patient was referred to our clinic with the chief complaint of incompatible dentures. The patient had been using the same complete dentures for 40 years. Extraoral clinical examination revealed protruded, bulged lower lip at rest and bilateral blepharochalasis, defined as atrophy of the upper eyelid skin. The upper lip and lower eyelids were not affected. Intraoral examination revealed complete edentation of both jaws and a double lower lip, an accessory fold of excess mucosae inside the vermillion border. Furthermore, epulis fissuratum was observed in the lower jaw. There was no family history of double lip. The patient stated that she had noticed another lip inside her lip for several years. As Ascher syndrome was suspected, the patient was referred to the endocrinology department for thyroid examination, and the non-toxic goiter diagnosis was confirmed. Surgical removal of the redundant tissues was necessary because of deficiencies in speech, chewing, and aesthetics. The excess tissues were excised by transverse ellipse incision technique. Dentists should be familiar with Ascher syndrome, as they may be the first physicians to encounter patients with double lip.