We described two patients with postoperative sternal osteomyelitis with mediastinal abscess who were successfully treated by omentopexy. One was a 15-year-old boy. Five days after accessory pathway division for Wolff-Parkinson-White syndrome, he was diagnosed as having sternal osteomyelitis. Cultures of the exudate yielded staphylococcus epidermidis. Closed continuous irrigation with diluted povidone-iodine was not effective. After open drainage, omentopexy with an omental pedicle flap was performed. Postoperatively, computed tomography showed no abnormal findings in the omental flap and surrounding tissue. The second patient was a 33-year-old man. Re-aortic valve replacement for aortic regurgitation was performed. Eleven days after the operation, he was diagnosed as having postoperative sternal osteomyelitis. Cultures of the drainage fluid yielded staphylococcus epidermidis. Continuous closed irrigation with povidone-iodine was ineffective. Thus, the wound was opened and omentopexy with an omental pedicle flap was performed. The postoperative course was uneventful. Computed tomography showed no residual abscess or recurrent inflammation. We conclude that the omentopexy is useful in the treatment of postoperative sternal osteomyelitis.