Heterotopic mesenteric ossification (HMO) is an uncommon disorder that may sometimes be misdiagnosed. It can cause bowel or intestinal perforation, which may also lead to serious complications or even death. Heterotopic bone formation in the omentum, which is called heterotopic omental ossification (HOO) and is one type of HMO, is considered to be an exceedingly rare event. To our knowledge, about 29 cases of HMO have been reported in previous studies, of which three were HOO. We herein describe a case of HOO occurring in a 39-year-old Chinese man with no medical history of abdominal surgery. He underwent a left hemicolectomy, which was performed for the treatment of descending colon adenocarcinoma. Two weeks later, he developed a small bowel obstruction associated with multiple foci of heterotopic bone formation within the omentum. He therefore underwent a second surgical procedure for adhesiolysis and a partial omentectomy. The postoperative course was uneventful. He is still alive and disease-free 16 months later.