Agenesis or hypoplasia of the hepatic lobe and floating gallbladder are both rare. We report an extremely rare case of hypoplasia of the left hepatic lobe accompanied by floating gallbladder. The patient was a 71-year-old woman, with no past history of related symptoms, who was admitted for further evaluation of postprandial epigastralgia, nausea, and diarrhea. Laboratory data on admission showed chronic liver disease with positive anti-hepatitis C virus antibody. Abdominal ultrasonography and computed tomography revealed the absence of the left hepatic lobe and displacement of the gallbladder to the left. On endoscopic retrograde cholangiography, the cystic duct originated from the right side of the bile duct, but the gallbladder was displaced to the left. Poor yolk-induced gallbladder contraction suggested the existence of hypotonic biliary dyskinesia. Angiography demonstrated no middle or left hepatic arteries, indicating congenital hypoplasia of the left hepatic lobe. Open cholecystectomy was carried out, and a diagnosis of hypoplasia of the left hepatic lobe accompanied by floating gallbladder and chronic hepatitis was confirmed. We believe that this is the first reported case of a hypoplasia of the left hepatic lobe coexisting with floating gallbladder.