Florid cemento-osseous dysplasia (FCOD) with concomitant simple bone cysts is not common. We report a case of FCOD involving three quadrants of the jaws and associated with two large cystic lesions of the mandible in a 40-year-old Japanese woman. Microscopic examination revealed unencapsulated fibroblastic proliferation with formation of bone and cementum, showing different developmental stages, and cystic lesions resembling a simple bone cyst.