Primary malignant melanoma of the esophagus is rare, accounting for less than 0.1–0.2% of all esophageal malignancies. It is associated with a poor outcome due to late detection and high metastatic potential. Here, we report a case of esophageal cancer, which was initially diagnosed as an adenocarcinoma and finally was confirmed as a primary malignant melanoma. This 75-year-old Caucasian male had a history of dysphagia and recent lingering abdominal pain. First biopsy showed a poorly-differentiated adenocarcinoma. He was then treated with neoadjuvant radiochemotherapy. Biopsies were repeated because of an incomplete tumor response, evaluated by endoscopic and imaging studies. The final diagnosis was a malignant melanoma. The patient has been treated with immune-checkpoint inhibitor, nivolumab, an anti-PD1 antibody.