Thymoma presenting concurrent pure red-cell aplasia (PRCA) and hypogammaglobulinemia are extremely rare. A 67-year-old woman with a short of breath was referred to our hospital due to anemia and the chest abnormal shadow. Laboratory investigations revealed a hemoglobin level of 5.6 g/dl and reticulocyte percentage of 0.2%. Her serum gamma-globulin level was low. Chest computed tomography (CT) revealed a 7-cm tumor in the left upper mediastinum. We diagnosed the patient with thymoma accompanied by PRCA and hypogammaglobulinemia. The patient underwent thymectomy and PRCA has been successfully treated by postoperative cyclosporine administration. Monthly intravenous infusion of gamma-globulin has been necessary for the control of hypogammaglobulinemia. Currently, she is doing well without recurrence of thymoma or PRCA five years after the surgery.