Background: The aim of this study was to investigate the incidence and risk factors of primary and secondary liver failure after major liver resection for perihilar cholangiocarcinoma. Methods: All patients who underwent a major liver resection for presumed perihilar cholangiocarcinoma between 2000 and 2020 at 2 tertiary-referral hospitals were included. Liver failure was defined according to the International Study Group for Liver Surgery criteria, and only grade B/C was considered clinically relevant. Primary liver failure was defined as failure without any underlying postoperative cause, and secondary liver failure was defined as liver failure with an onset after an underlying postoperative complication as a cause. Results: The incidence of liver failure and 90-day mortality were 20.9% and 17.0% in the 253 included patients, respectively. The incidences of primary liver failure was 9.1% and secondary liver failure was 11.9%. Abdominal sepsis, portal vein thrombosis, and arterial thrombosis were the most frequent causes. The absence of preoperative remnant liver assessment and blood loss were independent risk factors for primary liver failure. Independent risk factors for secondary liver failure were Eastern Cooperative Oncology group performance status, percutaneous biliary drainage, and preoperative cholangitis. Conclusion: Liver failure after major liver resection for perihilar cholangiocarcinoma occurred in 1 of every 5 patients. The proposed subdivision into primary and secondary liver failure could help to understand differences in outcomes between centers and help to reduce liver failure.