A 78-year-old woman was endoscopically followed up for benign melanocytosis in the middle thoracic esophagus that was detected 3 years prior. She presented with chest tightness, and an endoscopic examination revealed a protruding tumor at the melanotic lesion. She was histologically diagnosedwith an esophageal primary malignant melanoma. Computedtomography showedno metastatic lesions. She underwent minimally invasive esophagectomy with 2-fieldlymphad enectomy. Immunotherapy with nivolumab is ongoing for liver metastasis, which developed1 year and6 months after esophagectomy. Careful follow-up for esophageal melanocytosis is important for early diagnosis of esophageal primary malignant melanoma.