Osteosarcoma is the most common malignant tumor of bone. The mean age of occurrence of osteosarcoma in the jaws is around 30, somewhat older than for other sites in the body. These lesions occur about equally in the maxilla and mandible. They most frequently develop in the body in the mandible, and the antrum and the posterior portion of alveolar ridge in the maxilla. We report a case of osteosarcoma in 35 years old female complaining swelling of the left cheek. Radiographic features showed cotton wool appearance in upper left posterior area. Histopathologic findings exhibited pleomorphic malignant osteoblasts and neoplastic osteoid.