Descending necrotizing mediastinitis (DNM) is a highly fatal disease and as infection spreads along deep cervical planes into the mediastinum, widespread cellulitis, necrosis, abscess formation, and sepsis may occur. Early diagnosis is crucial for starting aggressive treatment without delay. Cervicothoracic computed tomography (CT) scanning may be useful for early diagnosis and preoperative evaluation of the surgical approach. Optimal treatment includes broad-spectrum antimicrobial therapy and extensive cervicomediastinal and transthoracic drainage. Clamshell incision provides an excellent exposure of both thoracic cavities and all mediastinal structures with minimal morbidity. We report here a fatal case of DNM with bilateral empyema and purulent pericarditis due to an odontogenic abscess with a brief review of the literature.