Left-sided gallbladder (LSGB) is a rare anomaly, but it is often associated with multiple combined variations of the liver anatomy. We present the case of a patient with LSGB who underwent successful resection of perihilar cholangiocarcinoma. The patient was a 67-year-old male who presented with upper abdominal pain and obstructive jaundice. Initial imaging studies led to the diagnosis of Bismuth-Corlette type IIIB perihilar cholangiocarcinoma. Due to the unique location of the gallbladder and combined multiple hepatic anomalies, LSGB was highly suspected. During surgery after hilar dissection, we recognized that the tumor was located at the imaginary hilar bile duct bifurcation, but its actual location was corresponding to the biliary confluence of the left median and lateral sections. The extent of resection included extended left lateral sectionectomy, caudate lobe resection, and bile duct resection. Since some of the umbilical portion of the portal vein was invaded, it was resected and repaired with a portal vein branch patch. Due to anatomical variation of the biliary system, only one right-sided duct was reconstructed. The patient recovered uneventfully without any complication. LSGB should be recognized as a constellation of multiple hepatic anomalies, and therefore, thorough investigations are necessary to enable the performance of safe hepatic and biliary resections.