Objective: We report a case of oligodendroglioma showing marked neuronal differentiation. Method: A 46-year-old female visited an emergency room because of an attack of convulsion. Imaging analyses disclosed a calcified, 3.5×3 cm tumor in the right frontal lobe. Results: The resected tumor was composed of a mixture of oligodendroglioma-like (OLG) and gangliocytoma-like (GC) areas. In the former, fried-egg appearance and more cellular nodules were recognized. In the latter, there were numerous small neuron-like cells with basophilic cytoplasm. OLG areas showed immunoreactivity for Olig2, GFAP and mutant IDH1, while GC areas were positive for synaptophysin and NeuN. Ki-67 labeling index was about 10 % in cellular nodules of OLG areas. At least one allelic loss of 1p/19q was detected in 53.4/61.2 % cells in OLG areas and 47.2/40.6 % in GC areas with FISH analyses. Furthermore, an identical mutation of IDH1 (G395A, R132H) was demonstrated in both OLG and GC areas.