We report a case of advanced gastric cancer that was successfully treated with second-line chemotherapy followed by curative conversion gastrectomy. The patient was a 71-year-old man. Endoscopic examination revealed a type 3 gastric cancer in the lower third of the stomach. Abdominal computed tomography (CT) revealed multiple lymph node metastases and metastasis to the peritoneal cavity. The clinical diagnosis was cT4N3aP1H0M1(LYM), cStage IV. The patient was treated with S-1 (80 mg/m² on days 1-28, every 6 weeks [q6w]) in November 2009. Temporarily, both the size of the primary lesion and the swelling of the lymph nodes were markedly reduced. However, after 10 courses of chemotherapy, the primary lesion was found to be enlarged again. The patient was then treated with S-1(80 mg/m², on days 1-14, every 6 weeks [q3w]) plus CPT- 11 (150 mg/m² on day 1, q3w) as the second-line chemotherapy. After 8 courses, an abdominal CT showed no peritoneal or lymph node metastases, but gastric endoscopy revealed the presence of a residual primary lesion. After staging laparoscopy, distal gastrectomy with D2 lymphadenectomy was performed. The histological diagnosis was ypT3 (SS) N1M0, Stage IIB. Analysis of the histological features of the primary tumor and peritoneal metastases resulted in their classifications as Grade 1a and Grade 3, respectively. After surgery, there were no serious adverse events. The patient has been in good health without recurrence for over 3 years after surgery.