Although rare, endogenous hypercortisolemia, including Cushing's disease (CD), is known to cause bowel perforation and to mask typical symptoms of bowel perforation, leading to delayed diagnosis. Additionally, elderly patients with CD are considered to be at a higher risk for bowel perforation because intestinal tissue fragility tends to increase in the elderly. Herein, we describe a rare case in which a young adult patient with CD was diagnosed with bowel perforation associated with CD following severe abdominal pain. A 24-year-old Japanese man was admitted to the hospital for the evaluation of ACTH-dependent Cushing's syndrome. He suddenly complained of severe abdominal pain on the 8th day of hospitalization. Computed tomography revealed free air around the sigmoid colon. The patient was diagnosed with bowel perforation, underwent emergency surgery, and was saved. He was subsequently diagnosed with CD, and the pituitary adenoma was resected transsphenoidally. To date, eight cases of bowel perforation due to CD had been reported, with a median age of 61 years at the time of bowel perforation. Hypokalemia was detected in half of the patients, and all had a history of diverticular disease. Nevertheless, not many patients complained of peritoneal irritation. In conclusion, this is the youngest reported case with bowel perforation due to CD and the first report of bowel perforation in a patient without a history of diverticular disease. Bowel perforation may occur in patients with CD, irrespective of age and the presence of hypokalemia, diverticular disease, or peritoneal irritation.