BACKGROUND Calvarial epidermoid cysts (EC) are encased remnants of ectoderm at the third week of gestation. There are also reports which consider them sequelae of head trauma. They are benign lesions. As they develop, they exert a mass effect to adjacent anatomical structures. CASE REPORT We report the case of a 58-year-old male patient with left-sided exophthalmos. His radiologic examinations depicted an oval cystic lesion (7×5×5.5 cm) arising from the left frontal bone and abutting the ipsilateral orbital roof. Our patient underwent a total extirpation of the lesion through a frontal craniectomy. Cranioplasty was then performed with a Porex® graft. The pearl-hued lamellae of the lesion macroscopically resembled keratin tissue. Histopathological findings supported the diagnosis of an epidermoid cyst. Postoperatively, our patient had no neurologic deficits and a computed tomography scan showed no residual effects. CONCLUSIONS Large calvarial EC with intraorbital expansion in adults are rare clinical entities. Gross total resection with the infiltrated bone and cranioplasty is the treatment of choice, which also establishes the diagnosis.