Leiomyoma is the most uncommon benign neoplasm of the breast. We report a case of a middle-aged woman with a palpable breast mass who underwent excisional biopsy. Pathologic examination revealed a leiomyoma. The clinical characteristics, pathologic findings, and proper management of this lesion are discussed. The tumor is thought to arise from the smooth muscle of the endothelium and can be managed similarly to leiomyomas occurring elsewhere. The possible effects of tamoxifen on uterine leiomyomas may be of theoretical concern with breast leiomyomas. The recognition of this entity and an understanding of the management of this rare lesion are necessary by all surgeons who perform breast surgery.