Although cases of simultaneous esophagus and stomach cancer have been reported sporadically, there are rare reports of successful treatment using chemotherapy. We report a case of synchronous esophageal and gastric cancer successfully treated using docetaxel and cis-diammineedichloro-platinum (CDDP) combination chemotherapy instead of surgery. A 82-years-old man with anorexia and progressive weight loss was diagnosed with synchronous esophageal and gastric cancer by endoscopy. Both cancers were diagnosed as resectable by the preoperative clinical staging. However, surgery was contraindicated because of severe lung dysfunction. Moreover, he actively refused radiotherapy and endoscopic management. Therefore, the patient was given combined chemotherapy with docetaxel (65 mg/m²) and CDDP (60 mg/m²). The esophageal and gastric lesion completely disappeared on endoscopy, and there were no residual tumor cells on endoscopic biopsy after three cycles of chemotherapy. Metastatic lymph nodes also completely disappeared on the CT scan. The patient received a total of ten cycles of chemotherapy, without severe adverse effects. The patient remained asymptomatic for 18 months after discontinuation of the chemotherapy, without evidence of local recurrence or distant metastasis. Surgery or endoscopic treatment of both esophageal and gastric cancers is desirable, but, if medically inoperable, chemotherapy can be alternative treatment option.