Emphysematous pyelonephritis is a rare, severe gas-forming infection of the kidney. Herein we report a case of a 51-year-old man who had received a cadaveric renal transplant 12 years ago. Post-transplant diabetes mellitus occurred 8 years later. He experienced urinary tract infection with graft pain one week before admission and presented with septic shock at the emergency room. Plain X-ray of the abdomen showed retroperitoneal air. A computed tomography scan of the abdomen showed retroperitoneal and extraperitoneal air being released from the graft kidney. These findings were compatible with extensive emphysematous pyelonephritis. The patient underwent percutaneous drainage. Blood culture and urine culture yielded Escherichia coli. After repeated percutaneous drainage and strong antibiotics for a prolonged period, the patient finally recovered.