<p>Probiotics, live microorganisms with health-promoting properties, play a vital role in modulating the gut microbiota and enhancing immune responses. Their potential for regulating key signaling pathways, including NF-κB, PI3K/AKT, and Wnt/β-Catenin, suggests promise in cancer prevention as they can mitigate inflammation, strengthen intestinal barriers, and influence cytokine production, offering multiple therapeutic benefits. This review highlights the mechanisms by which probiotics may contribute to gastrointestinal cancer prevention and treatment, discussing their capacity to regulate inflammatory cytokines, enhance epithelial integrity, and balance gut microbiota. Evidence from preclinical and a growing number of clinical studies is summarized. Additionally, challenges such as strain specificity, dose optimization, and safety evaluations are analyzed alongside potential integration into conventional cancer therapies. Current data indicate that probiotics hold potential as complementary agents in oncology, possibly capable of inhibiting tumor growth, enhancing immune surveillance, and improving the efficacy of existing treatments. Future research should prioritize robust, long-term clinical trials and molecular studies to optimize their application in cancer management.</p>