Abstract: Helicobacter pylori (Hp) is a common pathogenic bacterium in the human digestive system. It has been classified as a group I carcinogen by the International Agency for Research on Cancer under the World Health Organization in its published list of carcinogens. Immunotherapy has brought new hope to patients with gastric cancer; however, in clinical practice, there are substantial individual differences in the response, and the poor therapeutic effect in some patients remains a bottleneck that urgently needs to be addressed. In recent years, a growing number of studies have shown that HP infection may be deeply involved in regulating the efficacy of gastric cancer immunotherapy through unique pathways, such as reshaping the tumor microenvironment and regulating immune checkpoint molecules expression. Research in this interdisciplinary field offers a new perspective on analyzing the mechanisms of immunotherapy resistance and holds important exploratory value. This article systematically reviews the research progress on the impact of Hp on gastric cancer immunotherapy and its potential mechanisms, aiming to provide a theoretical basis and research directions to overcome therapeutic limitations and optimize individualized treatment strategies.