An 8-year-old boy presented with a germinoma of the right basal ganglia manifesting as gradual onset of mild left hemiparesis. Computed tomography (CT) and magnetic resonance imaging disclosed a mass lesion in the right basal ganglia with mild right cerebral hemiatrophy. Single photon emission CT revealed decreased cerebral blood flow in both the right cerebral and left cerebellar hemispheres, or crossed cerebellar diaschisis. The histology of a specimen from a stereotactic needle biopsy was compatible with two-cell pattern germinoma. After irradiation and chemotherapy, the mass lesion disappeared completely. The clinical symptoms and crossed cerebellar diaschisis gradually improved.