Hilar cholangiocarcinoma is considered a biologically aggressive disease for which surgical resection remains the only curative treatment . Preoperative evaluation for resectability is challenging given tumor proximity to the porta hepatis , but minimal benefit and increased morbidity precludes recommendation for margin positive resection. This article reviews the determination of unresectability in hilar cholangiocarcinoma through discussion of the preoperative assessment, the intraoperative assessment, and key steps of surgical resection, as well as treatment options for unresectable tumors. Overall, evaluating patients preoperatively for resectability requires a multidisciplinary, holistic, and individualized approach to accurately determine resectability and optimize clinical outcomes for patients with hilar cholangiocarcinoma.