Choristomas and mixed hamartomas of the oral cavity are uncommon lesions that show a variety of clinical presentations, histological appearances and growth patterns. We report a case of an unusual mixed hamartoma of the posterior tongue composed of dermoid cyst, sebaceous and glial elements. Magnetic resonance imaging indicated a predominantly cystic lesion limited to the pharyngeal and posterior part of the anterior tongue. A conservative approach was adopted and the lesion has shown minimal growth for 2 years following diagnosis.