Dermoid cysts located in the floor of the mouth are very rare developmental keratinizing squamous epithelium lined cysts. Anatomically, they are classified as sublingual (median genioglossal), submental (median geniohyoid) and lateral dermoid cysts, and they can be further classified as epidermoid, dermoid, and teratoid cysts by histology. We report a case of sublingual dermoid cyst in a 16-year-old boy presenting as a large sublingual swelling causing speech and swallowing difficulties and discuss the surgical treatment techniques and histopathological features of this lesion.