Dermoid cysts are anatomic embryonic abnormalities that are rarely seen in the oral cavity. Histologically, they are further classified as epidermoid, dermoid or teratoid. We report a case in which an 18- year-old girl who developed an epidermoid cyst presenting as a large sublingual swelling occupying the entire floor of the mouth causing snoring and speech difficulty. We emphasized on the clinical steps in achieving an accurate diagnosis, possible differential diagnosis, necessary imaging techniques and management of epidermoid cyst.