Simple hepatic cyst is usually asymptomatic and requires no treatment, and its complication, such as hepatic cyst infection, can occur. This report describes a 68-year-old man with a large simple hepatic cyst at left lobe diagnosed 2 months before hospitalization in computed tomography of abdomen examination. One week before admission, he received panendoscopy which revealed esophageal candidiasis in local clinics. Before this admission, he came to our outpatient clinic and presented with intermittent and aggravated epigastric pain and 6 kgs weight loss. He gave no history of fever, chills and bowel habit change. Physical examination revealed palpable mass, tenderness and tympanic sound on percussion at epigastric region. Abdominal standing X-ray film revealed a cavitary lesion with air-fluid level. A gas-forming infected hepatic cyst was highly suspected. Routine laboratory tests were unremarkable, except C-reactive protein showed 16.22 mg/ dl. Percutaneous transhepatic drainage of the cyst was made right away for further biological diagnosis and treatment. Milky yellowish fluid was obtained with fishy smelling odor. The drainage culture was Bacteroides capillosus. This is the first case report of infected hepatic cyst caused by the Bacteroides capillosus.  (J Intern Med Taiwan 2021; 32: 50-55)