This is the first report of a patient with acute transverse myelopathy as the initial manifestation of primary Sjögren's syndrome (SS). The patient developed tetraparesis and sensory disturbance within 6 days of onset. Spinal MRI showed an extensive intraparenchymal lesion with high T2-weighted signal intensity, gadolinium enhancement, and cord swelling. Although the patient did not show clinical sicca symptoms, primary SS was diagnosed on the basis of clinical tests on lacrimal and salivary glands which showed high levels of autoantibodies. Treatment with prednisone improved motor and sensory symptoms and resulted in improvement of MRI findings. The present case suggests that acute transverse myelopathy can occur as an initial symptom of SS.