We report a case of 15 year-old female patient with a ossified chronic epidural hematoma. She had had head trauma 10 weeks previously and conservative care for delayed onset epidural hematoma at other hospital. Ossification was identified about 4 weeks after head injury and then progressed rapidly. We removed the chronic epidural hematoma with thick capsule and newly formed bone. The mechanism of the ossification associated with cephalhematoma and chronic subdural hematoma is reviewed and discussed.