Primary osteosarcoma of the calvarium is rare. A 22-year-old female patient was admitted for a progressively enlarging, indurated mass under her scalp for 6 months. A computed tomographic scan revealed a 4 x 3 x 2-cm3 osteolytic lesion over the right parietal cortex with a sunburst appearance. The patient underwent en bloc tumor resection using bicortical parietal craniectomy with a 2-cm margin of normal bone, including the tightly adherent periosteum over the tumor. Immediate cranioplasty was performed with split-thickness autogenous calvarial bone grafts. Histopathologic examination showed the tumor to be a primary high-grade osteosarcoma of the skull. She received postoperative chemotherapy. She has recovered well and remains without any evidence of disease at her most recent, 8-year follow-up. The key to disease-free survival in treating primary osteosarcoma of the calvarium is complete surgical resection with immediate reconstruction followed by adjuvant chemotherapy.