© 2015 The Japanese Society of Gastroenterological Surgery. We report a case of delayed graft duodenal perforation 5 months after simultaneous cadaveric pancreas-kidney transplantation (SPK). A 45-year-old woman with insulin-dependent diabetes during over 20 years underwent SPK in August 2013. She was discharged on postoperative day 27 with normal pancreas and kidney function. Five months later, she was admitted to our hospital because of severe lower abdominal pain due to acute peritonitis and septic shock in January 2014. On emergency operation, perforation of the anastomosed site between graft duodenum and ileum was detected. Perforation was closed with primary suture and omentopexy. Intestinal fistula tube was placed for decompression of the graft duodenum. She was discharged on postoperative day 27 with normal pancreas and kidney function. At 11 months after this surgery, her pancreas and kidney function were stable (HbA1c: 5.4%, Serum creatinine: 0.74 mg/dl). Delayed graft duodenal perforation after SPK is rare.