Background: To examine the survival benefit of definitive concurrent chemoradiotherapy (CCRT) compared to radiotherapy alone in patients with esophageal squamous cell carcinoma (ESCC) using a real-world patient population. Methods: This retrospective study included 2,762 patients with ESCC across ten medical centers in China from 2001 to 2017. A total of 1,133 patients received radiotherapy alone and 815 patients were treated with CCRT. The patient survival rates were assessed by propensity-score matching (PSM) and subgroup analysis. Results: The baseline characteristics were significantly different between the two groups, with the CCRT group showing a higher proportion of males, younger patients, cervical/upper thoracic cancers, and worse T and N stages. There were no significant differences in the clinical characteristics between the two groups after PSM. Before PSM, the median overall survival (OS) rates were 31.2 and 24.1 months in the CCRT and RT alone groups, respectively, demonstrating the superior therapeutic effects (TEs) of the CCRT. However, the median OS rates were not significantly different between the two groups after PSM (32.6 and 39.4 months in the CCRT and radiotherapy alone groups, respectively). The subgroup analyses revealed that the median OS was significantly better in the CCRT group compared to the radiotherapy alone group (37.5 vs. 25.1 months, respectively) in patients less than 70 years of age [hazard ratio (HR) 0.782, 95% confidence interval (CI): 0.657 to 0.932]. In contrast, in patients 70 years of age and older, the 5-year survival rate was poorer in the CCRT group (34.8%) compared to the radiotherapy alone group (73.4%). Therefore, CCRT was an independent poor prognostic risk factor (HR 3.206, 95% CI: 2.168 to 4.740). Conclusions: CCRT may not be suitable for all patients with localized ESCC. Younger patients less than 70 years of age might benefit significantly from CCRT. However, in patients aged 70 years and older, the potential survival benefit of CCRT and the optimal combination treatment regimens require further investigation.