Osteosarcoma is the primary malignancy of bone. Osteosarcoma of the jaw (JOS) is very rarely encountered in the oral cavity compared to osteosarcomas of long bones. Therefore, general dentist should be aware of the initial clinical and radiographic findings. The chief complaint of patients with long bone osteosarcoma is pain, whereas patients with JOS usually have painless swelling as the first sign. Lack of pain may result in delay of diagnosis. This paper documents one such case of 40-year-old female with an expansile lesion of maxilla, which was completely asymptomatic and later diagnosed as osteosarcoma.