Thymic carcinomas are rare neoplasms, and standard treatment has not yet been established. We reported a case of advanced thymic carcinoma effectively treated by surgical resection and postoperative radiation therapy. A 71-year-old man was pointed out an abnormal shadow on chest X-ray. Chest computed tomography (CT) scan demonstrated an anterior mediastinal tumor. The tumor was diagnosed as carcinoma by CT-guided tumor biopsy and was extirpated completely with combined partial resection of the left lung. Microscopically, the tumor was diagnosed as thymic carcinoma with direct invasion to the left lung. Following postoperative radiation therapy, the patient is doing well without apparent recurrence 5 years after surgery.