We describe a case of sudden death caused by a rare complication of Crohn's disease. A 29-year-old man with Crohn's disease who had not taken medications regularly complained of nausea, vomiting, and abdominal pain for 2 days, and then died suddenly. Autopsy revealed protruding intestinal loops filled with gas, internal fistulas between fused loops of the terminal ileum, and complete obstruction of the fistulous tract. The histologic findings of transmural inflammation consisting of lymphocytic infiltration, accumulation of partially hyalinized collagen, and fibrosis in the skip areas from the ileum to the cecum were compatible with Crohn's disease. Furthermore, marked emaciation, atrophic change of the heart muscle, and diffuse fatty change of the liver were found. Although the patient died of obstructive ileus caused by a stricture produced by progression of Crohn's disease, he was severely affected by malnutrition which may have been fatal. This case not only illustrates that Crohn's disease can cause obstructive ileus and sudden death, but also makes the forensic pathologist realize the importance of suspecting the presence of an active inflammatory bowel disease in a patient with internal fistulas or malnutrition.