Torsion of the greater omentum is a rare condition of acute abdomen. We, herein, report a 37-year-old man, who presented to the emergency department with right lower abdominal pain, nausea, and fever. The initial clinical impression was acute appendicitis. Preoperative computed tomographic study showed a well-defined, fat-containing mass interspersed with soft-tissue strands in the right lower abdomen and pelvis, and it also induced partial obstruction of the small intestine. This mass was found in connection with a vertical rod of the omental vessels. Surgical exploration revealed torsion of the greater omentum with hemorrhagic infarction. Computed tomography (CT) is a useful imaging modality for making a specific diagnosis. An inflamed fat-containing mass with a vascular pedicle is characteristic for the torsion of the greater omentum.