The human gut contains a large number of microbial communities that form a symbiotic relationship with the host to maintain the stability of the internal environment. Probiotics are microorganisms that are beneficial for improving the microecological balance of the host and can enhance the health level and health status of the host. In recent years, the inhibitory effect of probiotics on tumorigenesis has attracted the attention of the scientific community. It has been found that probiotics can induce apoptosis in human gastric cancer cell line HGT-1 cells. By affecting metalloproteinase 9 activity and tight junction protein (ZO)-1, probiotics inhibit colon cancer cell invasion, improve the sensitivity of colon cancer cells to 5-fluorouracil-induced apoptosis, and improve postoperative functional recovery and quality of life of colon cancer patients; they also enhance antioxidant capacity and inhibit oncogene expression, thereby reducing the occurrence of aflatoxin B1-induced precancerous liver lesions. Possible mechanisms of probiotics against cancer include in situ release of their anticancer metabolites, leading to tumor growth inhibition and promoting apoptosis and differentiation of tumor cells. Recent research advances have made probiotics promising as a carrier of oncogene therapy to efficiently and specifically introduce various therapeutic molecules into target cells or tissues, i.e., bacterial-mediated anticancer therapy. Research on probiotics and gastrointestinal tumors has brought new opportunities for the prevention and treatment of gastrointestinal tumors, but most of the data in this area are from cellular and animal tests, and the conclusions of human epidemiological data are still controversial. Therefore, effective human studies are still needed to clarify the role of probiotics in the prevention and treatment of digestive tumors.