A 73-year-old man diagnosed as having pancreatic body cancer with multiple liver metastases was referred to our hospital. Since the patient preferred oral agents, S-1 monotherapy (4-week administration followed by 2-week interval) was started. The initial dose of S-1 was 80 mg, and gradually increased to 150 mg/day. There were no significant adverse events. The liver metastases disappeared and the pancreatic tumor was markedly reduced in size at the completion of 4 courses. Distal pancreatectomy was carried out at 7 months since his first visit. Pathological diagnosis was non-functioning well-differentiated neuroendocrine carcinoma (pT4, pN0, pM0, Stage IVa). He is alive without relapse 6 months after operation. S-1 might be a candidate for chemotherapy for this neuroendocrine tumor.