Different treatment strategies are required for the non-muscle-invasive, muscle-invasive, and metastatic stages of bladder cancer. Standard treatments include surgery, chemotherapy, and radiation
however, they have their limitations. New discoveries have shown that combining immunotherapy and radiation treatment may improve patient outcomes. Radiation therapy promotes immunogenic cell death, which leads to antigen release and immune cell activation, whereas immunotherapy enhances the immune system's ability to recognize and destroy cancer cells by targeting checkpoint pathways like PD-1/PD-L1 and CTLA-4. This review examines the synergistic mechanisms of diverse modalities, focusing on their capacity to alter the tumor microenvironment and elicit systemic anti-tumor responses, such as the abscopal effect. Key clinical trials, such as BTCRC-GU15-023 and ANZUP, have demonstrated the efficacy and safety of combining these medications. However, difficulties persist, such as overlapping toxicities, unpredictability in patient responses, and a lack of accurate patient selection markers. Large-scale randomized trials are needed in the future to fine-tune treatment procedures, minimize toxicity, and validate predictive biomarkers such as PD-L1 expression and tumor mutation burden. By addressing these hurdles, the combination of radiation treatment and immunotherapy has the potential to change the bladder cancer therapeutic landscape.