We report a case of perforated jejunal diverticulitis in a 68-year-old man with iatrogenic Cushing's syndrome. The patient presented with right upper abdominal pain. Ultrasonography showed a hypoechoic structure connected to a small bowel loop, and subsequent CT examination showed multiple diverticula in proximal jejunal loops with free air trapped within the mesenteric leaf. Segmental resection of the jejunal loop confirmed jejunal diverticulitis with perforation.