Pigmented mammary Paget's disease is a rare variant of mammary Paget's disease. The clinical appearance mimics malignant melanoma. This paper describes a case of asymptomatic, slightly pigmented spots on the right mammary nipple. The pigmented nipple was histopathologically diagnosed as mammary Paget's disease with an underlying intraductal carcinoma. This case suggests the importance of conducting skin biopsies of developing pigmented spots on the nipples in elderly people.