A diagnosis of intestinal diverticulosis is difficult to make pre-operatively because the clinical symptoms are usually non-specific. We report the case of a 70-year-old man who had suffered from three episodes of intestinal obstruction in 1 year. He experienced dull pain and a sensation of fullness over the whole abdomen. The symptoms did not improve after conservative treatment. The presumptive diagnosis was intestinal obstruction, and an exploratory laparotomy found diverticulosis of the proximal jejunum, with an adhesion band formed from the base of one diverticulum. Strangulation of a segment of the jejunum resulted from the internal herniation caused by the band. The band was removed and the proximal jejunum segmentally resected. His postoperative course was uneventful.