Primary calvarial or intra-osseous meningiomas are uncommon lesions often confused preoperatively with other primary or secondary bone tumors of the skull. We present details of a patient with a primary calvarial meningioma involving the frontal, zygomatic, sphenoid and temporal bones that was radiographically diagnosed as fibrous dysplasia and initially treated conservatively for many years. Progressive vision loss and significant proptosis, with difficulty of eye closure, prompted surgical removal with cranioplasty and a 3D reconstructed prosthetic flap. Histological examination revealed intra-osseous meningioma. The clinical and radiological findings of intra-osseous meningiomas are discussed, together with a review of the literature.