Background: Several studies have highlighted the prognostic value of the albumin-globulin ratio (AGR) in various kinds of cancers. Our study was designed to assess whether AGR is associated with the prognosis of gastric cancer patients. Patients and methods: A total of 507 gastric cancer patients between 2005 and 2012 were included. The AGR was defined as the ratio of serum albumin to nonalbumin and calculated by the equation: albumin/(total protein -albumin). Furthermore, AGR was divided into two groups (low and high) using the X-tile software. Survival analysis stratified by AGR groups was performed. Results: The mean survival time for each group was 36.62 months (95% CI: 33.92-39.32) for the low AGR group and 48.95 months (95% CI: 41.93-55.96, P=0.003) for the high AGR group. Patients in the high group (AGR >= 1.93) had a significantly lower 5-year mortality in comparison with the low group (AGR<1.93) (52.4% vs 78.5%, P= 0.003). The high AGR group showed obviously better overall survival than the low AGR group according to Kaplan-Meier curves (P= 0.003). Multivariate analysis showed that AGR was an independent predictive factor of prognosis in gastric patients. Conclusion: Pretreatment AGR is a significant and independent predictive factor of prognosis.