Angiomatosis is a benign vascular lesion that has been described rarely in the breast. We describe a case in a seven-year-old boy of African descent who presented with progressively increasing, unilateral breast enlargement, the first such report in a male child. The patient underwent excisional biopsy of the breast mass followed by mastectomy. Pathologic examination revealed a diffuse proliferation of variably-sized, thin-walled vascular channels lined by flattened endothelium that showed negative immunohistochemical staining for von Willebrand factor, factor VIII-related antigen, CD34 and S-100 protein. There is no evidence of recurrence after 24 months of follow-up.