In this report, we describe the case of a patient with splenic marginal zone lymphoma (SMZL) who presented with spastic paraplegia as the initial symptom. A 42-year-old male developed progressive spastic paraplegia over 4 months. His neurologic examination revealed paraplegia with pyramidal syndrome, hypoesthesia below the T1 level, and anal hypotonia. Magnetic resonance imaging (MRI) of the spinal cord revealed an extensive high-intensity signal in T2-weighted sequences and swelling involving the thoracic region and conus medullaris. A laboratory test revealed presence of the serum M component. Abdominal computed tomography images showed moderate splenomegaly. Abnormal lymphocytes of B-cell lineage markers (CD19+, CD20+, and CD25+; surface immunoglobulin κ expression; IgD+ and IgM+) were found in the peripheral blood, cerebrospinal fluid, bone marrow and spleen. Splenectomy confirmed the SMZL diagnosis. After the completion of chemotherapy, the patient was in complete remission, and spinal MRI findings were normal. Intramedullary spinal cord involvement in SMZL is extremely rare, and, to the best of our knowledge, this is the first case of SMZL with intramedullary spinal cord involvement associated with clinical and radiologic signs without the involvement of cerebral structures. Spastic paraplegia can be the initial presentation of SMZL.