A 15-year-old boy presented with an anaplastic supratentorial ependymoma causing massive intratumoral calcification, without contributory medical and family history, and manifesting as persistent headache for 2 months. Physical examination found no neurological deficit except for visual defect in the right lower quadrant, with intact visual acuity. Blood examination showed no abnormalities. Cranial computed tomography revealed a huge calcified mass in the left parietooccipital lobe, with extensive perilesional brain edema. Cranial radiography showed diffuse and symmetrical thinning of the calvarial bone. Magnetic resonance imaging confirmed the tumor as an assembly of medullated masses with extraventricular location, 7 × 6.5 × 6.5 cm in diameter, and appearing as heterogeneous intensity on both T1- and T2-weighted images with inhomogeneous enhancement except for the central cores. The patient underwent tumor resection. Intraoperative findings revealed that the cortical veins overlying the tumor were reddish and moderately engorged. The hypervascular tumor, entirely extraventricular in location, was totally resected without neurological deterioration. Histological examination revealed that the tumor was highly cellular with hyperchromatic nuclei and cell atypia. Necrosis, mitotic figures, and perivascular pseudorosette formations were frequently seen. Immunohistochemical study showed positive staining for glial fibrillary acidic protein, S-100 protein, vimentin, and epithelial membrane antigen, but negative for synaptophysin. The MIB-1 labeling index was 26.5%. The findings were compatible with anaplastic ependymoma (World Health Organization classification grade 3). Ependymoma should be included in the differential diagnosis of a supratentorially located, extraventricular mass with massive intratumoral calcification.