The hypertrophy of the lingual tonsil is a rare occurrence in adults. This disorder may cause obstructive sleep apnea (OSA) and also may lead to a life-threatening obstruction of the upper airway. Diagnosis of lingual tonsil hypertrophy in patients with OSA requires a careful examination by advanced technologic methods. The sleep apnea is successfully treated by lingual tonsillectomy, with or without tracheotomy. In this study the case of an adult with OSA caused by lingual tonsil hypertrophy which was treated with lingual tonsillectomy is presented, and the diagnosis and the treatment procedure of such cases are discussed.