Aims and background: The International Union Against Cancer tumor node metastasis classification is routinely applied for evaluating the prognosis of patients with gastric cancer. However, results are still heterogeneous. This study was therefore carried out to evaluate the prognostic significance of the metastatic lymph node (LN) ratio in T3 gastric cancer patients undergoing gastrectomy. Methods: Clinical data of 109 LN-positive cases were retrospectively analyzed. Spearman correlation analysis was used to determine the correlation coefficiency. Survival time was determined by Kaplan-Meier and Log-rank test. Multivariate analysis was performed using the Cox model. ROC curves were used to compare the accuracy of the number of metastatic LN and metastatic LN ratio. Results: The metastatic LN ratio did not correlate with the number of LN when at least 15 nodes were dissected, whereas the number of metastatic LN did. Univariate analysis showed that the metastatic LN ratio influenced significantly the survival time, while multivariate analysis revelaed it to be a major independent prognostic factor. Conclusions: The metastatic LN ratio can be used as a major independent prognostic factor for the patients with T3 gastric cancer.