Involvement of the choroid plexus by malignant lymphoma is rare. This case showed mass lesions at the choroid plexus in the first stage of systemic non-Hodgkin's malignant lymphoma. A 53-year-old female was admitted with headache, diplopia, and gait disturbance. The patient was alert but had left supraclavicular and axially lymph node swelling. Computed tomography scan revealed enhanced masses at the lateral and fourth ventricles. The lymph node biopsy disclosed non-Hodgkin's malignant lymphoma, diffuse large cell type. The immunological marker was the B-cell type. At surgery, there was highly vascular white tumor at the choroid plexus of the right lateral ventricle. The tumor also involved adjacent brain tissue. Pathological examination revealed infiltration of lymphoma cells to the choroid plexus. The subependymal and perivascular spaces of the choroid plexus were filled with lymphoma cells. Virchow-Robin space and white matter of adjacent brain tissue were also involved by lymphoma. After surgery, whole brain irradiation of 35 Gy and chemotherapy were performed. However, 14 months after initial diagnosis, the patient expired because of systemic involvement by the lymphoma.