This study aimed to derive a more precise estimate of the prognostic significance of S-1-based therapy over S-1 monotherapy in patients with advanced gastric cancer (AGC), including overall survival (OS) time, progression-free survival (PFS) time, objective response rate (ORR), and adverse events (AEs). Studies stratifying OS, PFS, ORR, and AEs in AGC patients in an S-1-based therapy versus an S-1 monotherapy setting were eligible for analysis by systematic computerized PubMed, Embase and Cochrane Library searches. Data from these studies were pooled using STATA package version 11.0. Six studies that investigated outcomes in a total of 913 AGC cases, of which 443 (48.5%) received S-1-based therapy and 470 (51.5%) received S-1 monotherapy, were included in the meta-analysis. Median OS and median PFS were significantly prolonged in AGC patients receiving S-1-based therapy compared with those receiving S-1 monotherapy (hazard ratio [HR] 0.83, 95% confidence interval [CI] 0.71-0.96, P = 0.015, and HR 0.69, 95% CI 0.60-0.80, P = 0.000, respectively). The ORR favored patients with S-1-based therapy (OR 1.65, 95% CI 1.34-2.06, P = 0.000). Higher incidence of grade 3/4 neutropenia was found in patients with S-1-based therapy (P = 0.000). For the Asian population, S-1-based therapy significantly improved OS and PFS and enhanced ORR in comparison to S-1 monotherapy. The safety profile was poorer in patients with S-1-based therapy, but could be considerable between the S-1-based therapy and S-1 monotherapy group. Our conclusion needs to be confirmed via high-quality trials and the results need to be reproduced in other regions and populations.