Pneumoperitoneum reflects intra-abdominal visceral perforation in 85 to 95 % of all occurrences. In 5 to 15 % of cases, however, pneumoperitoneum does not reflect perforation and results from another source. Herein, we report a rare case of surgery indicated pneumoperitoneum caused by the rupture of gas-containing pyogenic liver abscess (GPLA) in a newly-diagnostic diabetic 57-year-old man. He presented the symptoms mimicking intra-abdominal visceral perforation. He recovered uneventfully after surgical intervention, drainage, full-course of antibiotics and strict control of blood glucose. Cultures of blood and ascites grew Klebsiella pneumoniae.