Retractile mesenteritis is a rare idiopathic inflammatory process of the mesenteric adipose tissue. A 58-year-old woman who presented with acute abdominal pain and vomiting underwent laparotomy for a small bowel obstruction of unknown etiology. The laparotomy showed dilated small bowel loops and multiple tumor-like fibrous plaques in the mesentery. Histological examination revealed nonspecific chronic inflammatory processes of the mesentery. The computed tomography finding of increased density of the mesenteric fat, known as the "fat-ring sign," in a patient with small bowel obstruction and no surgical history would suggest this rare diagnosis.