A 67-year-old woman presented with an acute onset of left-sided weakness. Magnetic resonance (MR) imaging revealed multiple cerebral infarctions and gadolinium-enhanced lesions in both cerebral hemispheres. Her symptoms once improved after starting steroid treatment; however, soon developed consciousness disturbance and hemiparesis on the left side. She was referred to our hospital where she underwent stereotactic needle biopsy, that revealed an intravascular large B-cell lymphoma in the cerebrum. She received high-dose methotrexate chemotherapy followed by whole-brain radiation therapy, and the MR findings improved. However, her medical condition gradually worsened, and she died 6 months after disease onset. Intravascular lymphoma (IVL) limited to the central nervous system (CNS) is very rare, and the optimal treatment for this medical condition has not been established yet. IVLs showing only neurologic manifestations might be overlooked or misdiagnosed as cerebral infarctions. Here, we present a case of CNS IVL, with its radiographic and pathologic features and treatment with high-dose methotrexate chemotherapy.