Thymic carcinoma is a rare but aggressive neoplasm. Although there is no clearly optimal first- or second-line chemotherapy regimen for thymic carcinoma, platinum-based chemotherapy has repeatedly been shown to be of benefit to patients with advanced thymic carcinoma. Some case reports have described S-1 as a novel agent with good activity against advanced thymic carcinoma. A 74-year-old female was diagnosed with thymic carcinoma complicated by pleural dissemination and pericardial effusion of carcinomatosa. She was treated with carboplatin on day 1 plus S-1 on days 1-14 in cycles repeated every 3 or 4 weeks. Four cycles of this regimen were administered, and a partial response was confirmed. There were no severe hematological or nonhematological toxicities, and no dose reduction was necessary. To our knowledge, this is the first report to demonstrate the efficacy of combination chemotherapy consisting of carboplatin and S-1 against thymic carcinoma.