IgG4-related sclerosing disease of the breast is a rare entity with 10 reports in the literature. We report the first case in a male patient. A 48-year-old male presented with 4-week history of palpable right upper outer quadrant breast mass associated with skin puckering. He reported a family history of breast cancer in his aunt. Ultrasound and mammography showed a spiculated 2.5-cm mass associated with skin retraction with extension to the pectoralis muscle. Ultrasound-guided core biopsy was performed. The findings were interpreted as acute and chronic inflammatory process. The patient subsequently denied improvement of the mass, and an excisional biopsy was performed. Histologic examination showed fibrosis and dense lymphoplasmacytic inflammation in the breast mass and muscle biopsy. Focal obliterative phlebitis was noted. IgG4-positive plasma cells were increased with counts of over 50 per high-power field. The diagnosis was confirmed as sclerosing IgG4-related disease of breast.