Collagenous fibroma is a recently described rare benign tumor that mainly affects those in the fifth through seventh decades. It is a painless solitary mass, which grows slowly for more than 6 months, up to 20 cm. Several cases were reported chromosomal rearrangements with a breakpoint at 11q12. Histopathologically, it shows well-circumscribed mass that consists of scattered stellate cells in hypovascular collagenous matrix without atypia or mitosis. Management method is excision with functional preservation. In Korea, only two cases of collagenous fibroma have been reported so far. A 69-year-old woman was presented to our clinic with two painless well-demarcated hard masses, 4.5×4.5 and 4.5×2.5 cm in size, on both anterior superior iliac spine. Traumatic injury or a previous event was not noticed by the patient. After histopathologic examination, those masses were diagnosed as collagenous fibroma.