Primary malignant melanoma of the mediastinum is extremely rare : To date, there have been only 8 cases reported in the literature. We report a case of a 50-year-old woman presented with an anterior mediastinal mass. The mass invaded the lung parenchyme of right upper lobe, which was wedge-resected with the mass. Microscopically, spindle or polygonal tumor cells with prominent nucleoli and intracytoplasmic melanin pigments are characterized and Fontana stain confirmed the presence of melanin pigment. Immunohistochemical studies showed diffuse positive staining for HMB45, S100 protein and vimentin, which further suggested melanoma.