We report the case of a 43-year-old man who presented with painless proptosis of the right eye of 6 weeks' duration. Examination demonstrated a tense right orbit and decreased vision and extraocular motility bilaterally. Diagnostic evaluation included computed tomographic imaging of the head and orbits, a therapeutic trial of high-dose systemic corticosteroids, and orbital biopsy, which revealed the presence of metastatic adenocarcinoma. The primary tumor was found to be an estrogen-receptor-positive, infiltrating ductal adenocarcinoma of the right breast. Therapy included lumpectomy of the breast mass, orbital irradiation, and hormonal therapy. Metastatic carcinoma of the breast should be considered in the differential diagnosis of orbital neoplastic disease in the male patient.