Gastric cancer represents one of the most common malignant tumors worldwide and leading cause of cancer-related mortality. The emergence of immune checkpoint inhibitors (ICIs) has markedly influenced the therapeutic landscape of gastric cancer in recent years. Programmed cell death protein-1 and ligand 1 (PD-1/PD-L1) inhibitors not only demonstrate significant survival benefits in the first-line treatment of advanced gastric cancer, but also provide new strategies for perioperative management of locally advanced gastric cancer. This artical aims to outline the application of ICIs in first-line and perioperative treatment of gastric cancer, and to discuss key issues including mechanisms of resistance, management of immune-related adverse events, and heterogeneity of the tumor microenvironment. These insights may shed light on novel immunotherapeutic strategies, optimization of combination regimens, and advancement of precision and individualized treatment approaches.