A 69-year-old man presented for endoscopic examination of the upper gastrointestinal tract because of dysphagia for solid food and unintended weight loss. Several months before, he had noticed brownish-gray skin lesions in the neck, in the thorax and in both axillae. A dermatological consultant expressed the suspicion of a paraneoplastic disease. Endoscopic examination revealed an adenocarcinoma of the esophagogastric junction as well as multiple small polyps in the middle and the lower thirds of the esophagus. Histological examination showed papilloma-like proliferations without atypia, which were diagnosed as acanthosis nigricans of the esophagus. After completion of the staging investigation regarding the cardiac carcinoma, combination chemotherapy was started because of the presence of liver metastases. Subsequently, partial regression of the carcinoma as well as of the dermal and esophageal lesions was noted. Acanthosis nigricans is a rare paraneoplastic disease of the esophagus. As an indicator lesion, its detection should prompt a search for a malignant tumor in the gastrointestinal tract.