The study analyzed the clinical data of 793 patients with gastric cancer in stages pT2-4, where the value of pan-immune inflammation (PIV) serves as a new prognostic biomarker. The optimal cut-off value of PIV was determined using ROC analysis to divide patients into high and low PIV groups. PIV demonstrated better predictive value for progression-free survival (PFS) and overall survival (OS) than other peripheral blood immuno-inflammatory biomarkers. High PIV was significantly associated with Helicobacter pylori infection, larger tumor size, and advanced TNM stage. Patients with high PIV, especially in stages III and IV, had significantly worse PFS and OS according to Kaplan-Meier curves. In multivariate Cox regression analysis, PIV was confirmed as an independent prognostic factor for survival. PIV is more sensitive to tumor burden and systemic inflammation than other assessed biomarkers. The study highlights the clinical value of PIV for patients with pT2-4 gastric cancer.