A 77-year-old man was admitted to our hospital on a diagnosis of acute mediastinits, 17 days after he had high fever. Computed tomography of the chest revealed an abscess cavity in the left upper mediastinum. Endoscopic examination showed multiple pin-hole perforations in the upper esophagus from 23 to 24cm distal from the incisors and drainage through the perforation. We diagnosed acute mediastinitis caused by multiple esophageal perforations of unknown etiology. We initiated conservative therapy. Oral intake was restarted on the 17th day because radiological examination showed the esophageal perforation had closed. The patient was discharged on the 36th day from admission. Although mediastinitis caused by esophageal perforation often demands surgical treatment, conservative nonoperative therapy was successful in this patient.