Supernumerary breast or polymastia is a well documented anomaly of the breast, and commonly presents along the embryonic milk line extending between the axilla and groin. However, cases of polymastia have been recorded in the face, vulva and perineum. The clinical significances of these anomalies include their susceptibility to inflammatory and malignant changes, and their association with other congenital anomalies of the urinary and cardiovascular systems. The present article reports a case of fibroadenoma developing in the supernumerary breast of the right axilla in a 28 year old woman. Clinical and mammography examination of both breasts revealed no abnormalities and no lymph nodes were detected in the axillae or the neck. No associated urologic or cardiovascular abnormalities were found, and the histopathological examination of the excisional biopsy samples showed a well-defined, capsulated intracanalicular type of fibroadenoma similar to that of eutopic mammary tissue. The article also outlines the common congenital anomalies of the breast, and emphasizes on their proper clinical assessment for any other associated anomaly together with adequate surgical excision and regular follow up of the treated patients.