Desmoid fibromatosis (DF) of the breast is a rare condition. Owing to its rarity and mimicry of carcinoma, the diagnosis and optimal treatment of DF are challenging tasks. A 41-year-old woman with no history of augmentation or other breast procedures for breast cancer was examined. The patient had a palpable mass in the left breast identified as a spiculated hypoechoic mass using ultrasonography. Core needle biopsy revealed spindle cells without mitotic figures. The mass was excised and a histopathological examination confirmed the diagnosis of DF. The patient had no history of any related factors. Imaging studies did not reveal specific features that could distinguish this tumor from other commonly presenting carcinomas. Therefore, pathological confirmation is of paramount importance for the diagnosis of DF. Further experience with more cases will help to understand DF better and develop a multidisciplinary approach to its clinical management.