The patient was a 73-year-old man. We have performed an ascending aortic prosthesis replacement for a thoracic aortic aneurysm complicated by idiopathic thrombocytopenic purpura (ITP). The platelet count was not sufficiently increased neither by preoperative Helicobacter pylori (H. pylori) eradication nor corticosteroid therapy. After treatment with high-dose intravenous gammaglobulin (400 mg/kg/ day×5 days) and the use of thrombopoietin receptor agonists, the platelet count increased to 8.9×104/ μl and the operation was safely performed. With a steady increase in platelet count, the patient continued to do well post-operatively. We report a case in which a stable platelet count was achieved throughout the perioperative period by the effective combination of high-dose intravenous gammaglobulin and a thrombopoietin receptor agonist in a patient with ITP refractory to corticosteroid therapy.