AbstractThe effectiveness of neoadjuvant immune checkpoint inhibitor (ICI) therapy is confirmed in clinical trials; however, the patients suitable for receiving this therapy remain unspecified. Previous studies have demonstrated that the tumor microenvironment (TME) dominates immunotherapy; therefore, an effective TME classification strategy is required. In this study, five crucial immunophenotype‐related molecules (WARS, UBE2L6, GZMB, BATF2, and LAG‐3) in the TME are determined in five public gastric cancer (GC) datasets (n= 1426) and an in‐house sequencing dataset (n= 79). Based on this, a GC immunophenotypic score (IPS) is constructed using the least absolute shrinkage and selection operator (LASSO) Cox, and randomSurvivalForest. IPSLowis characterized as immune‐activated, and IPSHighis immune‐silenced. Data from seven centers (n= 1144) indicate that the IPS is a robust and independent biomarker for GC and superior to the AJCC stage. Furthermore, patients with an IPSLowand a combined positive score of ≥5 are likely to benefit from neoadjuvant anti‐PD‐1 therapy. In summary, the IPS can be a useful quantitative tool for immunophenotyping to improve clinical outcomes and provide a practical reference for implementing neoadjuvant ICI therapy for patients with GC.