Gangliogliomas are rare tumors of the central nervous system, usually containing neoplastic ganglion cells and astrocytic components. Few cases of ganglioglioma containing only oligodendrocytic tissue have been reported to date. We present a case of a 40-year-old woman with ganglioglioma consisting mostly of oligodendroglial components. Magnetic resonance imaging showed a well-demarcated cystic lesion with slight perifocal edema in the right parietal lobe. The wall of the cyst was not enhanced after administration of Gd-DTPA contrast media. The mass was totally resected. Histological examination showed a mixture of two distinct components: oligodendroglioma and dysplastic ganglions. The first component was diffusely proliferated cells with round nuclei and perinuclear halo; the second showed marked nucleoli and basophilic cytoplasm containing Nissl bodies. Immunohistochemical study of the oligodendroglial component was positive for OLIG 2 and NKX2.2 but negative for synaptophysin. In addition, LOH of 1p/19q was detected by FISH. Although no adjuvant therapy was carried out, follow-up MRI showed no recurrence of the tumor 41 months after the operation.