Single-agent or combined chemotherapy with the novel oral fluoropyrimidine anticancer drug, S-1 (TS-1), has been reported to be useful for the treatment of advanced gastric cancer. Here, we report a patient with advanced gastric cancer achieving a complete response (CR) after 2 weeks of administration of S-1 as neoadjuvant chemotherapy. A 78-year-old woman with epigastric pain was diagnosed as having advanced gastric cancer. S-1 was administered orally, at a dose of 50 mg twice a day every day for 2 weeks, followed by a 2-week drug-free period. No obvious adverse reactions occurred. Subsequently, the patient underwent distal partial gastrectomy with D2 lymph node dissection. Pathological examination indicated no remnant signet-ring cells in the excised specimen, no lymph node metastasis, and unnatural fibrosis in one of the No. 3 lymph nodes. The neoadjuvant chemotherapy induced a CR according to the Japanese classification of gastric carcinoma.