NAD(P) H:quinone oxidoreductase-1 (NQO1) confers resistance to anticancer agents, particularly to oxidative stress inducers such as cisplatin or 5-fluorouracil in malignant tumors. Here we evaluated the association between NQO1 expression in esophageal squamous cell carcinoma (ESCC) cells and the patients' responses to preoperative chemotherapy with cisplatin and 5-fluorouracil (CF), and we elucidated the prognostic significance of NQO1 expression in ESCC patients. We retrospectively analyzed the cases of 40 patients who underwent preoperative CF therapy followed by curative esophagectomy with lymphadenectomy. Immunohistochemistry of the surgically resected specimens was conducted using the primary monoclonal antibody against NQO1. Eighteen of the 40 patients (45%) had tumors that showed high NQO1 expression (NQO1-high group). The poorer histological response to preoperative CF therapy was dominant in the NQO1-high group compared to the NQO1-low group (72% and 45%, respectively) but the difference was not significant (P=0.09). The 3-year recurrence-free survival rate after esophagectomy in the NQO1-high group was significantly lower compared to the NQO1-low group (39% vs. 76%; P<0.01). A Cox proportional hazards model revealed that high NQO1 expression was an independent unfavorable prognostic factor (HR=3.53; P=0.02) as was pN3 (HR=14.7; P<0.01). The immunohistochemical evaluation of NQO1 expression has potential to predict the treatment response and prognosis in patients who undergo preoperative CF therapy followed by esophagectomy for ESCC.