Objectives: The classification of pathological tumor-node-metastasis (pTNM) staging of gastric cancer was revised in the 8th American Joint Committee on Cancer (AJCC) edition. The major revision was the separation of pN3a and pN3b in the pTNM staging. The current study evaluated the prognostic impact of this change. Methods: A total of 1,517 patients who underwent curative surgery for gastric cancer with a retrieved lymph node number 15 at our institution from January 1995 to December 2011 were enrolled. Survival was compared for the disease classified according to both the 7th and 8th editions. Results: After separation of pN3a and pN3b in the pTNM stage definition, the 8th edition still provides significant survival differences between each stage. The multivariate analysis demonstrated that the pTNM stage in both the 7th and 8th editions was an independent prognostic factors of overall survival and disease-free survival. The 8th edition has a better homogeneity than the 7th edition with a significantly higher likelihood ratio chi-square test. Regarding the OS and DFS, the time-dependent receiver operating characteristic (ROC) curves of the two staging systems are almost overlapping, indicating that the prognostic performance is comparable between the two staging systems. Conclusions: Both the 7th and 8th edition-based stages are independent prognostic factors for gastric cancer. The 8th edition has a better homogeneity than the 7th edition; the 8th edition provides discriminant survival differences among each pTNM stage that are comparable to those in the 7th edition.