Although ossifying fibroma (OF) is a slow growing neoplasm, some lesions may behave aggressively, reaching massive proportions that may demand special treatment. Synchronous presentation of this lesion in the maxilla and mandible is a rare occurrence. A case is presented of a 27-year-old woman who manifested synchronous OF lesions in the left maxilla and right mandible. The clinico-radiologic and histopathologic modalities of diagnosing OF are evaluated and discussed.