III, were the primary and secondary outcome measures, respectively. The severe postoperative complications and mortality rates were 28.4% (23/81) and 11.1% (9/81), respectively. Patients with preoperative biliary drainage had significantly lower bilirubin concentrations (p = 0.028) than did those without. The preoperative bilirubin concentration was a risk factor of postoperative mortality (p = 0.003), with an optimal cut-off of 6.20 mg/dL (c-statistic = 0.829). The preoperative bilirubin concentration was a risk factor of severe morbidity (p = 0.018), with an optimal cut-off of 2.48 mg/dL (c-statistic = 0.662). These results indicate that preoperative hyperbilirubinemia is a major risk factor of negative early postoperative outcomes of patients who undergo surgical treatment for hilar cholangiocarcinoma and may aid in decision-making with respect to preoperative biliary drainage.