Gastric cancer (GC) is a leading cause of cancer-related deaths worldwide, and therapeutic options for advanced GC are limited. Here, we observe that intratumoral microbiota controls chemokine expression, which in turn recruits immune cells into the tumor, and that immune infiltration is strongly associated with patient survival and disease attributes. Furthermore, microbiota regulation of chemokines is differentiated in GC patients with different survival risks. As seen in gastric tumors, in high-survival-risk patients, Pseudomonas regulates CCL4, CXCL9, CXCL10, and CXCL11 accumulation to recruit immune cells such as CD4