An 84-year-old woman was admitted to our hospital with high fever, and she suddenly complained of severe abdominal pain the next day. Computed tomography revealed a gas-containing abscess in the lateral segment of the liver, with spontaneous pneumoperitoneum. An emergency lateral segmentectomy was performed, and Klebsiella pneumoniae was cultured from the liver tissue, abscess, and blood. The patient made a satisfactory recovery and was discharged on the thirty-first postoperative day. Pneumoperitoneum caused by the rupture of a gas-containing liver abscess is rare, and to our best knowledge, this is the first report, in the English-language literature, of a patient who has undergone successful hepatectomy for such a condition.