A 38-year-old Japanese male was referred to our hospital with abnormal chest X-ray results and severe Coombs-positive hemolytic anemia. He was diagnosed with a stage IV, WHO type A thymoma and was treated with oral prednisolone (1 mg/kg/day) and subsequent chemotherapy. After chemotherapy, the patient underwent surgical resection of the thymoma. Hemolysis rapidly disappeared and did not return after the discontinuation of oral corticosteroids. Corticosteroid therapy may be preferable to chemotherapy or thymoma surgical resection in the management of autoimmune hemolytic anemia with thymoma.