A 47-year-old man with thymic carcinoma that had invaded the inner pericardium and adhered to the superior vena cava and right atrium at first operation was treated with intra-arterial infusion chemotherapy (nedaplatin and adriamycin) through the internal thoracic artery. After 2 courses of modified ADOC therapy (nedaplatin, adriamycin, vincristine, and cyclophosphamide), chest computed tomographic (CT) scans revealed a 47% reduction in tumor size. No adverse effects due to the anticancer drugs were observed. Resection of the tumor included part of the upper lobe of the right lung and pericardium. Examination of resected tumor tissue specimens revealed viable cancer cells and extensive fibrosis. The diagnosis was thymic anaplastic carcinoma. We concluded that intra-arterial selective infusion chemotherapy utilizing an ADOC regimen can be of value as a treatment for thymic carcinoma.