Descending necrotizing mediastinitis is a life-threatening complication of an oropharyngeal infection that requires prompt and aggressive medical and surgical therapy. Herein, we report unusual case of man suffering of sub-acute mediastinal infection due to odontoiatric abscess which exacerbated at 3 months after its first presentation. Chest X-ray and CT scan demonstrated soft-tissue swelling of the neck and encapsulated fluid collections with gas bubbles within anterior mediastinum, especially on the right side. Bilateral anterior neck dissections were performed and blunt dissection, irrigation and debridement were carried out to several centimetres below the sternal manubrium. Then, right standard thoracotomy was performed with debridement of the anterior mediastinum. Four tubes were placed in the mediastinum and pleural cavity on the right side, and two tubes were placed in the left thoracic cavity. Follow-up CT scans of neck and chest showed the resolution of infection.