Despite the application of conventional therapies,the prognosis of advanced gastric cancer (GC) or gastroesophageal junction cancer (GEJC) is still poor.In recent years,immune checkpoint inhibitors (ICIs) have reshaped the paradigm of cancer therapy.Emerging evidence support the feasibility of programmed cell death-1 (PD-1) and its ligand (PD-L1) inhibition in chemo-refractory GC/GEJC.Nivolab and pembrolizumab have initially been approved in Japan and United States,respectively for the third-line treatment of progressive GC or GEJC.In March 2020,nivolumab has also been licensed in China for treating advanced GC/GEJC who received ≥ 2 lines of systemic therapies.Current studies are moving forward to the first-line application or focusing on combination strategies,though data are insufficient and disputable.In this review,we summarize the recently reported and ongoing clinical trials in ICIs for advanced GC/GEJC.Molecular characteristics and clinical implications of different tumor subtypes are also reviewed.We further discuss the safety profile and biomarkers for predicting the response of ICIs,which has guiding values in clinical practice.