OBJECTIVE To investigate the prognostic significance of body mass index (BMI) on the survival of patients with esophageal squamous cell carcinoma (ESCC) after esophagectomy. METHODS Between 2005 and 2008, 291 patients with ESCC who met the inclusion criteria were included in the study. The BMI cut-off values were as follows: 18.5-23 kg/m2 for normal weight; 23-27.5 kg/m2 for overweight; and ≥27.5 kg/m2 for those with obesity. Univariate and multivariate analyses were performed to identify prognostic factors for long-term survival. RESULTS Patients were divided into 3 groups: normal weight (n = 138), overweight (n = 103), and obese (n = 50). The median survival time was 56 months. The 5-year overall survival (OS) rates were 40.8, 44.7, and 20.8% for normal weight, overweight, and obese patients respectively (p < 0.05). Multivariate analysis identified BMI as an independent prognostic factor for OS (p < 0.05). For 179 patients without lymph node metastasis, the 5-year OS rates were 46.5, 50.7, and 27.0% for normal weight, overweight, and obese patients respectively (p < 0.05). CONCLUSIONS A BMI ≥27.5 kg/m2 has a distinctly adverse impact on the long-term survival of ESCC patients after esophagectomy. High BMI is a potential predictor of worse prognosis in ESCC patients, particularly in patients without lymph node metastasis.