We aimed to assess the efficacy and safety of S-1 combined with cisplatin (SC) over cisplatin alone (C) for the treatment of advanced gastric cancer in China. Between July 2009 and June 2011, 72 eligible patients with advanced gastric cancer were selected and divided randomly into two groups. Thirty-six patients received SC, with S-1 on days 1 through 14 of a 21-day cycle and cisplatin (60 mg/m on day 1) every 4 weeks for two cycles. The other 36 patients were administered only cisplatin (in the same manner as SC). The primary outcome was overall survival. The secondary outcomes were progression-free survival and adverse events. The 2-year overall response rate was 51.5 and 42.3% for the SC and C groups, respectively, and the difference was statistically significant, whereas the median overall survival was 9.4 months (range, 1.9-24.4 months) and 7.6 months (range, 1.7-21.4 months), respectively (P=0.039). The median progression-free survival was 7.7 months for SC (range, 1.8-19.4 months), whereas it was 6.5 months (range, 1.5-16.4 months) for C (P=0.047). The toxicity profile was similar in both groups. In summary, we have shown that S-1 combined with cisplatin is more effective, with acceptable toxicity in comparison with cisplatin alone in Chinese patients with advanced gastric cancer. Chinese Clinical Trials Register: ChiCTR-TRC-13003993.