A 69-year-old man complained of a sore throat, neck swelling, and disturbance of swallowing with dyspnea. He underwent tracheostomy and cervical drainage. The plain chest roentgenogram and CT scans suggested mediastinitis, so he was transferred to our hospital. Cultures revealed a mixed aerobic and anaerobic infection. On hospital day 2, the neck was explored and pus was found in the connective tissue. Despite drainage and intravenous panipenem with betamipron and clindamycin, he remained febrile and a mediastinal abscess was seen on repeat CT. On hospital day 10, reexploration of the mediastinum was done through cervical and right thoracotomy incisions. A large amount of pus was drained from the posterior mediastinum and its necrotic tissue was debrided. Myocardial infarction occurred intraoperatively, but the patient was successfully resuscitated. Following this procedure, the patient's condition and radiologic findings gradually improved. Cultures of the drain fluid became negative, and he was discharged on hospital day 103. In conclusion, both transcervical drainage and aggressive mediastinal exploration via thoracotomy are essential to salvage a patient with descending necrotizing mediastinitis. CT scanning is useful for early diagnosis of mediastinitis and for follow up.