Mediastinitis is a rare, progressive, and destructive infectious process due to cervical or odontogenic infections, which, if not diagnosed early, may lead to several complications, including airway involvement and even an imminent risk of death. Herein, we report an unusual case of a 37-year-old male with a bilateral submandibular hard swelling after the left third molar extraction. After surgical intervention with submandibular drainage and antibiotic therapy, the infection persisted without explanation, since the patient was not hypertensive, did not have diabetes mellitus or sexually transmitted infections such as HIV or syphilis, and did not smoke or drink alcoholic beverages. A thoracic surgeon then intervened, treating the mediastinitis surgically by drainage, thus obtaining a significant improvement of the patient’s health. Mediastinitis is a serious condition. Clinicians and maxillofacial surgeons should be alert to make an immediate diagnosis and select the appropriate treatment in order to prevent worsening of the patient’s clinical condition.