Thymoangiolipoma is a rare, slow-growing, benign thymic neoplasm that arises from the anterior mediastinum. A 61-year-old man with the chief complaint of right eye ptosis and high serum acetylcholine receptor antibody level is presented here. The spiral computed tomography of the chest revealed a hypodense mass in the anterior mediastinum. Microscopic examination showed admixture of adipose tissue, thymic tissue and blood vessels with the diagnosis of thymoangiolipoma. Thymoangiolipoma is a rare histologic variant of thymolipoma which can be associated with myasthenia gravis and must be considered as a differential diagnosis in anterior mediastinal mass with fat density in radiologic evaluation.