Background: This study aimed to determine the impact of weight loss during neoadjuvant chemoradiotherapy on the survival of patients with esophageal carcinoma. Methods: We retrospectively examined 102 consecutive patients with esophageal carcinoma who underwent neoadjuvant chemoradiotherapy followed by radical resection at Sichuan Cancer Hospital & Institute between 2003 and 2017. The patients were divided into three groups based on the amount of body weight lost during neoadjuvant chemoradiotherapy: severe weight loss (>10%), high weight loss (5%–10%), and low weight loss (<5%). The correlations of weight loss with toxicity, progression-free survival, and overall survival were investigated. Results: The median overall survival was 49.7 months in the low weight loss group compared with 35.4 and 25.1 months in the high and severe weight loss groups (P = 0.041). The 1-year overall survival rates in the severe, high, and low weight loss groups were 62.5%, 85.0%, and 90.7%, respectively; the corresponding 3-year overall survival rates were 21.9%, 47.3%, and 68.8%, respectively, and the corresponding 5-year overall survival rates were 21.9%, 31.0%, and 44.4%, respectively. The multivariate analysis indicated that a pathological complete response and severe weight loss were independent prognostic factors for overall survival. Any leukopenia (P = 0.024), leukopenia of at least grade 3 (P = 0.021), and anemia (P = 0.042) occurred more frequently in the severe weight loss group. Conclusions: Weight loss during neoadjuvant CRT is an independent and adverse prognostic factor in esophageal carcinoma patients, whereas a stable weight confers a better prognosis. Keywords: esophageal cancer, prognosis, weight loss, neoadjuvant chemoradiotherapy, toxicity.