BACKGROUND: The combination of radiation with immune checkpoint inhibitors (ICIs) has been demonstrated to display synergistic effects in solid cancers. Nevertheless, the anti-tumor effect of combining radiation with programmed cell death 1 ligand 1 (PD-L1) inhibitor in esophageal squamous cell carcinoma (ESCC) has remained unclear. Therefore, the objectives of our study were to evaluate the anti-tumor effects of PD-L1 inhibitors combined with radiotherapy in a mouse model of ESCC and to depict the immune landscape within the tumor microenvironment (TME). METHODS: Murine ESCC cells (mEC25) were injected subcutaneously into the right flanks of C57BL/6 mice. Tumor-bearing mice were exposed to different treatments: IgG antibody (control), anti-PD-L1 antibody, radiation, or radiation + anti-PD-L1 antibody. Tumor growth and survival time of mice were monitored. Tumour immune microenvironment was assessed by flow cytometry, including CD4 RESULTS: Radiotherapy combined with anti-PD-L1 inhibitors (radioimmunotherapy) synergistically enhanced anti-tumor immune response, leading to decreased tumor growth and prolonged survival of tumor-bearing mice. The radioimmunotherapy increased the infiltration of CD8 CONCLUSIONS: Our research revealed that anti-PD-L1 inhibitors combined with radiotherapy caused systemic anti-tumor immunity by reshaping the immune microenvironment in a mouse model of ESCC.