Primary malignant melanoma of the vagina, a very rare malignancy, is very aggressive and highly metastatic. Primary vaginal melanoma usually has a poor clinical prognosis, because it is often diagnosed at an advanced stage. We present a case of an 80-year-old postmenopausal woman with pigmented lesion of the vagina. The histopathology of the lesion revealed malignant melanoma. The patient was treated surgically, with wide local excision of the vaginal lesion. Left inguinal lymphadenectomy, based on the positron emission tomography-computed tomography (PET-CT) images, found metastatic melanoma. We present a case report of postmenopausal woman with primary vaginal melanoma.