Abstract: Tumor immunotherapy has achieved breakthroughs in the treatment of malignant tumors by activating the host immune system’s antitumor response mechanism. Among various strategies, Toll-like receptor (TLR) agonists have garnered substantial attention due to their unique immunomodulatory capabilities. This work reviews the research progress on the combination of TLR agonists with radiotherapy in tumor immunotherapy, focusing on the clinical translational potential of intratumoral injection strategies. Clinical studies have shown that the in-situ injection of TLR agonists in combination with radiotherapy can effectively suppress primary and metastatic lesions by inducing immunogenic cell death, releasing tumor antigens, activating local immune responses, and triggering abscopal effects. Moreover, novel extended-release formulations and “endogenous vaccine” designs further enhance the safety and durability of treatment. Despite several challenges such as tumor microenvironment suppression and dose optimization, TLR agonists hold promise for the treatment of “cold” tumors lacking innate immunity through combinations with immune checkpoint inhibitors, nanodelivery technologies, and precise biomarker screening.