Dysembryoplastic neuroepithelial tumors (DNETs) are considered as low-grade tumors commonly associated with intractable seizures. We report a case of an unusual hemispheric DNET in a young child presenting with new-onset focal seizures. The tumor was notable for its atypical neuroimaging features and very rapid malignant transformation into a glioblastoma multiforme in the absence of radiation or chemotherapy, 1-year postdiagnosis. Our case highlights the malignant potential of atypical DNETs in the absence of therapy.