We herein report an extremely rare case of a 55-year-old Japanese woman with a primary malignant melanoma of the esophagus associated with adenocarcinoma of the lung. The patient was admitted to our hospital with a malignant melanoma of the lower esophagus. The chest X-ray and computed tomography (CT) findings revealed an incidental abnormal shadow in the left lung, which was diagnosed to be adenocarcinoma of the lung by means of a CT-guided needle biopsy. After administering systemic chemotherapy with dacarbazine (DTIC), vincristine sulfate (VCR), and nimustine hydrochloride (ACNU) plus interferon-beta, the esophageal tumor markedly decreased in size. Subsequently, the patient underwent a radical resection of both the malignant melanoma of the esophagus and lung cancer via a left thoracotomy and laparotomy.