An 80-year-old Japanese man was admitted to our hospital in April 2016 with an acute high-grade fever and back pain. A systemic contrast-enhanced computed tomography scan disclosed a retroperitoneal abscess around his aorta. The blood culture revealed Klebsiella pneumoniae. Antibiotics (Cefotaxime 1 g i.v. q 6 hours) were administered, but the patient's symptoms worsened. The abscess then ruptured the aorta. An emergency surgical repair was done, and the patient recovered. Invasive Klebsiella pneumoniae syndrome has been detected in southeast Asia over the past two decades, and here we describe a rare case of a retroperitoneal abscess caused by Klebsiella pneumoniae that ruptured the aorta.