Gastric cancer is the second most common cause of cancer-related death in the world. A growing body of evidence indicates that inflammation is closely associated with the initiation, progression, and metastasis of many tumors, including those of gastric cancer. In addition, approximately 60% of the world's population is colonized by Helicobacter pylori, which accounts for more than 50% of gastric cancers. While the role of inflammation in intestinal and colonic cancers is relatively well defined, its role in stomach neoplasia is still unclear because of the limited access of pathogens to the acidic environment and the technical difficulties isolating and characterizing immune cells in the stomach, especially in animal models. In this review, we will provide recent updates addressing how inflammation is involved in gastric malignancies, and what immune characteristics regulate the pathogenesis of stomach cancer. Also, we will discuss potential therapeutics that target the immune system for the efficient treatment of gastric cancer.