We herein report a 12-year-old girl with a basal ganglia germinoma who presented with right-sided hemiparesis after a minor head trauma. Magnetic resonance (MR) imaging revealed a minimally enhanced lesion involving the left putamen, thalamus, and corona radiata. The lesion showed low-signal intensity on T1-, and high intensity on T2- and diffusion-weighted imaging. The MR signal in the adjacent globus pallidum was also low on T2-weighted imaging. MR spectroscopy on the lesion showed a large lactate/lipid/macromolecule peak with a decreased NAA/Cr ratio, but no increase in the Cho/Cr ratio. However, posttraumatic infarction at the territory of lateral lenticulostriate artery was ruled out 1 month later. This was based on progression of the hemiparesis and neuroimaging results, including an increased Cho/Cr ratio and weak uptake on (11)C-methionine positron emission tomography of the basal ganglia lesion. Stereotaxic brain biopsy confirmed the diagnosis of germinoma.