We reported a resected case of thymolipoma, which has been hardly experienced. The patient was 21-year-old female and consulted a doctor for general fatigue. Chest roentgenogram revealed a mass-like shadow at the right lower mediastinum, which was suspected mediastinal tumor. The mass of right anteroinferior mediastinum, which was clearly shown by chest CT scan and MRI, was continued to the right lobe of the thymus. Under a diagnosis of anterior mediastinal tumor, operation was carried out. The tumor, which was 10 x 8 x 7 cm in diameter and 160 g in weight, was removed together with right lobe of the thymus. Histological diagnosis of thymolipoma was obtained from the resected specimen.