Glioblastoma multiforme (GBM) is the most common lethal primary central nervous system tumor in adults. GBM is rarely seen in childhood and adolescence as primary intraventricular tumors. Few cases of solitary intraventricular GBM in adolescence have been reported to date. We report a 16-year-old boy with progressive disorientation, diffuse headache, vomiting, and increased intracranial pressure. Computed tomography and magnetic resonance imaging confirmed that the tumor filled posterior body and occipital horn of the left lateral ventricle and also invaded the surrounding parenchyma. Incomplete removal of the lesion was achieved and a pathologic diagnosis of GBM was carried out. We present a case with an uncommon subtype of glial tumor (GBM) in childhood located in a very rare site. The clinical course, radiologic findings, and possible treatment regimens are reviewed.