We report a rare case of strangulated ileus caused by knotting of the ileum in Meckel's diverticulum. A 41-year-old man with no history of surgery visited our hospital due to sudden severe abdominal pain and vomiting. Abdominal contrast-enhanced computed tomography showed a dilated small intestine with a closed-loop sign and ascites in the Douglas pouch. We considered it to be a strangulated ileus and performed an emergency operation. Intraoperative findings showed that the ileum was strangulated due to a knot in a long blind pouch and caused intestinal necrosis. We untied the knot and resected the blind pouch with the necrotic intestine, and end-to-end anastomosis was performed. Macroscopic findings showed that the resected specimen of the blind pouch (9.5 cm) was located approximately 50 cm from the end of the ileum on the opposite side of the mesenteric attachment site. Histopathological examination revealed that the blind pouch was Meckel's diverticulum. We finally diagnosed strangulation of the ileum due to knot formation in Meckel's diverticulum.