Probiotics are live microorganisms which confer a health benefit to the host when present in the correct amounts. They can be ingested as medications or dietary supplements to help maintain a balance in the microbial environment of the digestive tract. Probiotics can help maintain homeostasis and enhance physical fitness, thereby reducing the adverse effects caused by anti-cancer treatments. Recent studies have shown that probiotics can protect against and alleviate radiation-induced intestinal damage by activating anti-apoptotic pathways via AKT, inhibiting the COX-2 pathway to inhibit inflammatory reactions, protecting the intestine’s barrier function, improving bacterial translocation, and regulating the intestinal micro-environment. Although relevant clinical trials of probiotics have varied in terms of the bacterial species examined, the concentrations of live bacteria administered, and in the research methods used, most have demonstrated that probiotics could prevent radiation-induced adverse effects on the intestines. With the continuous improvements in the comprehensive treatment of cancer, the survival of patients has been prolonged. Therefore, in recent years, there has been increasing interest in ways to alleviate the adverse reactions and pain dur ing and after treatment and to improve the quality of life for patients. Future research should focus on optimizing the probiotic flora(type(s), numbers, and frequency of administration) and addressing the safety of probiotics for immunocompromised patients.