Malignant fibrous histiocytoma (MFH) is the most common type of soft tissue sarcoma, but it rarely develops as a primary tumor in the breast. Furthermore, no case of the myxoid variant of MFH in the breast has ever been documented. We report the case of a 52-year-old woman with a breast tumor that was immunohistochemically confirmed to be myxoid MFH. She underwent a radical mastectomy and is currently well with no evidence of local recurrence or metastatic spread after 3 years of follow-up.