This study aimed to evaluate the association between the immunohistochemical expression of NAD(P) H: quinone oxidoreductase-1 (NQO1) and nuclear factor erythroid 2-related factor 2 (Nrf2) in resected specimens of intrahepatic cholangiocarcinoma (ICC) and to elucidate the prognostic value of NQO1 and Nrf2 expression. A retrospective analysis was conducted of 34 consecutive patients who underwent surgical resection for ICC. Immunohistochemistry of the resected specimens was conducted using each of the following primary monoclonal antibodies against NQO1 and Nrf2. Of the 34 patients, 23 were classified as having tumors with NQO1-positive expression and 11 had tumors with loss of NQO1 expression, whereas 22 patients had tumors with Nrf2-positive expression and 12 had tumors with loss of Nrf2 expression. NQO1 expression showed a positive association with Nrf2 expression (p=0.005). Loss of NQO1 expression was more frequent in tumor specimens that were moderately or poorly differentiated (11/26; 42%) than in well-differentiated tumors (0/8; 0%; p=0.034). Post-resection survival was significantly worse in patients with tumors with loss of NQO1 expression than in patients with NQO1-positive tumors (cumulative 5 -year survival rate of 0% and 51%, respectively; p=0.005). Nrf2 expression was not associated with survival after resection (p=0.287). The Cox proportional hazards regression analysis revealed that lymph node involvement (p<0.001) and loss of NQO1 expression (p<0.001) had an independent adverse effect on survival. Loss of NQO1 expression reflects dedifferentiation and thus indicates a poor prognosis for patients undergoing resection for ICC.