Partial splitting of the upper sternum provides an excellent surgical view in reconstruction of the intrathoracic trachea. However, when deep-seated mediastinitis develops postoperatively, it is difficult to manage especially when combined with sternal osteomyelitis. It also needs an additional consideration compared to the usual treatment modality applied to mediastinitis following a standard median stemotomy because the lower part of the stemum remains intact. We treated a 50 year old female patient with deep-seated mediastinitis and sternal osteomyelitis following resection and end-to-end anastomosis of the trachea through an upper midline sternotomy. The patient underwent extensive stemectomy, omental free grafting, and pectoral myocutaneous flap. Postoperative viability of the free-grafted omentum was evaluated by angiography and CT scan.