A 47-year-old man was admitted to our hospital for treatment of an odontogenic infection. He presented with a fever, signs of sepsis, and neck swelling, and was initially diagnosed as having a neck abscess. After cervical drainage, he showed no improvement, and mediastinitis was detected by chest X-ray and computed tomography. A thoracotomy and mediastinal drainage was subsequently performed for descending necrotizing mediastinitis, which resulted in marked improvement. To date, only 83 cases of descending necrotizing mediastinitis have been reported in Japan. We present herein an additional case, followed by a review of the Japanese literature.