Background: The relationship between body mass index(BMI) and outcomes after chemoradiotherapy(CRT) has not been systematically addressed. The purpose of this study was to evaluate the effect of BMI on survival in patients with esophageal squamous cell carcinoma (ESCC). Materials and Methods: Sixty ESCC cases were retrospectively reviewed in this study. Patient overall survival(OS) and disease-free survival (DFS) were compared between two groups (BMI< $24.00kg/m^2$ and $BMI{geq}24.00kg/m^2$). Results: There were 41 patients in the low/normal BMI group (BMI< $24.00kg/m^2$) and 19 in the high BMI group ($BMI{geq}24.00kg/m^2$). No significant differences were observed in patient characteristics between these. We found no difference in 2-year OS and DFS associated with BMI (p=0.763 for OS; p=0.818 for DFS) using the Kaplan-Meier method. Univariate analysis revealed that higher clinical stage was prognostic for worse 2-year OS and DFS, metastasis for 2-year OS, lymph node status for 2-year DFS, while age, gender, smoking, drinking, tumor location and BMI were not prognostic. There were no differences in the 2-year OS (hazard ratio=1.117; p=0.789) and DFS(hazard ratio=1.161; p=0.708) between BMI groups in multivariate analysis, whereas we found statistical differences in the 2-year OS and DFS associated with clinical stage, gender and tumor infiltration (p<0.04), independent of age, smoking, drinking, tumor location, the status of lymph node metastases and BMI. Conclusions: BMI was not associated with survival in patients with ESCC treated with CRT as primary therapy. BMI should not be considered a prognostic factor for patients undergoing CRT for ESCC.