Primary malignant melanoma originating in the small bowel is extremely rare. We report the case of a 55-year-old man who presented with a preoperative bleeding duodenal tumor. A standard pancreaticoduodenectomy was performed. Histopathological examination ascertained the diagnosis of a duodenal malignant melanoma with locoregional lymphatic spread. A thorough postoperative investigation did not reveal any primary melanotic lesions. Thus, the diagnosis of a primary melanoma originating from the duodenum was suggested. Fourteen months after surgery, the patient had no evidence of recurrence. Primary malignant melanoma of the duodenum is an existing, though unusual, oncologic entity. Aggressive surgery remains the treatment of choice offering both symptom palliation and long-term survival.