Myofibroblastoma is a rare benign mesenchymal tumor of the breast. It presents as a well circumscribed, solitary nodular mass, and it has been reported to mainly occur in male patients. To our knowledge, few reports have described the radiologic appearance of myofibroblastoma in the female breast and there has been no report from Korea. We describe the mammographic, sonographic and histologic findings of a case of myofibroblastoma that presented as a well defined mass mimicking fibroadenoma in a 44-year-old woman.