The Inflammatory Burden Index (IBI) has been reported as a novel prognostic indicator in several cancers and diseases. However, research on the IBI in patients with gastric cancer (GC) after gastrectomy is insufficient. This study investigated the utility of the preoperative IBI as a prognostic indicator in patients with GC. This retrospective study enrolled 459 patients undergoing gastrectomy for GC between 2013 and 2017 at the Kanagawa Cancer Center, Kanagawa, Japan. The IBI was calculated from preoperative blood test data. We evaluated the relationship between the preoperative IBI and clinicopathologic factors, overall survival (OS), and recurrence-free survival (RFS) after gastrectomy for GC, using propensity score matched analysis. Regarding the association between IBI and clinicopathologic features, the high-IBI group was significantly older and had more lymphatic invasion and more progressive pT status than the low-IBI group before propensity score-matched analysis. OS and RFS after curative surgery were significantly lower in patients with a high IBI than in those with a low IBI (77.5% vs. 86.1%; p=0.02 and 74.3% vs. 85.1%; p=0.03, respectively). Multivariate analysis identified high IBI as an independent predictor of both OS and RFS. Preoperative IBI may serve as a valuable prognostic indicator for patients undergoing curative gastrectomy for GC.