A 78-year-old man complained of dysphagia. Gastrointestinal endoscopy showed a Type 2 tumor in the lower esophagus and a Type 0-Ⅱa lesion in the posterior wall of the upper gastric body. An enhanced CT scan showed several swollen abdominal and cervical lymph nodes as well as bilateral lung multiple nodules, suggesting distant metastasis. We diagnosed the patient with double cancers consisting of an unresectable advanced esophageal squamous cell carcinoma with multiple lymph nodes and lung metastases(Lt, cT3N4M1, cStage Ⅳb)and early gastric cancer(U, post, cType 0-Ⅱa, cT1N0M0, cStageⅠ). On day 4 of the first course of chemotherapy(docetaxel plus cisplatin plus 5-FU: DCF), a high fever was observed. A chest CT scan revealed suspected mediastinitis and right pyothorax due to perforation by the esophageal cancer. Thoracoscopic mediastinal drainage was immediately performed. CT-guided abscess drainage was added for a residual abscess in the right thoracic cavity on day 10 after drainage surgery. The patient's general condition improved, and he was discharged on 24th postoperative day. The patient was able to reinstitute and continue DCF therapy until disease progression.