The validity of the 8th edition of the Union for International Cancer Control (UICC) staging system for gastric cancer has been evaluated only in Asian cohorts and not in European cohorts. The aim of this study was to evaluate the prognostic performance of the 8th edition of the UICC staging system in German and Korean cohorts independently and compare it with that of the 7th edition.A total of 6121 patients (526 from Germany and 5595 from Korea) who underwent upfront surgery for gastric cancer were retrospectively reclassified according to the 8th edition. Survival according to the UICC stages was estimated by the Kaplan-Meier method and compared by log-rank tests. A Cox proportional hazards model was fitted after adjusting for clinicopathological factors, and receiver operating characteristics analysis was conducted.The 8th edition showed significant differences in survival between each adjacent stage in the Korean cohort but not in the German cohort. Multivariate analyses revealed that the 8th edition staging was an independent prognostic factor, and its C-statistics were >0.76 in both German and Korean patients. The results were comparable to those observed with the UICC seventh edition (C-statistics was 0.768 vs 0.767 in the German cohort and 0.789 vs 0.785 in the Korean cohort for the 7th vs the 8th edition).The 8th edition showed prognostic value in predicting the survival of gastric cancer patients in both German and Korean cohorts. However, the predictive ability of the 8th and 7th edition was similar.