Objective This study was designed to investigate the efficacy and prognostic factors for immune checkpoint inhibitors (ICIs) combined with or without radio(chemo)therapy and to evaluate their toxicity in patients with locally advanced or recurrent/metastatic esophageal squamous cell carcinoma (LA/RM ESCC).Methods In this study, 198 patients with locally advanced or recurrent/metastatic (LA/RM) ESCC who received ICIs combined with or without radiotherapy/chemotherapy in the Department of Radiotherapy of the Fourth Hospital of Hebei Medical University were retrospectively analyzed. Univariate and multivariate analyses were performed to determine the prognostic factors for overall survival (OS) and progression free survival (PFS). The factors affecting treatment response and the occurrences of treatment-related adverse events (trAEs) were analyzed.Results The median OS and PFS were 30.4 months (95% confidence interval [CI] 15.1-45.7 months) and 15.3 months (95% CI 12.8-17.8 months), respectively. Univariate and multivariate analysis showed that the number of ICI cycles, the intervention of radiotherapy and dysphagia were independent factors affecting OS (Hazard ratio [HR] = 0.39, 2.043 and 0.365, respectively; P = 0.018, 0.001 and 0.032, respectively). The intervention of radiotherapy was an independent factor for PFS (hazard ratio [HR] = 18.149, P = 0.013). The median OS and PFS for patients who had complete response and partial response (Objective response, ORR) were 50.8 months (95% CI 25.8-75.7 months) and 20.5 months (95% CI 14.1-27.0), respectively, which were significantly higher than those in the non-ORR group (OSnon-ORR:17.5 months, 95% CI 14.0-21.0; ?2 = 13.881, P < 0.001; PFSnon-ORR: 12.1 months, 95% CI 10.1-14.1, ?(2) = 10.676, P = 0.001). The intervention of radiotherapy could improve treatment response (?(2) = 47.725, P = 0.000). In entire study population, 83 patients (41.9%) had = grade 2 trAEs.Conclusions ICIs combined with radiotherapy/chemotherapy are safe and effective in LA/RM ESCC patients. Intervention of radiotherapy, the number of immunotherapy cycles and occurrence of dysphagia affecting the overall survival of LR/RM ESCC patients. Intervention of radiotherapy was an independent prognosis factor for OS and PFS and associated with better treatment response.