We report a rare case of mumps myelitis in which parotid swelling appeared 3 days after the symptoms of myelitis. A 10-year-old boy presented with acute paraplegia of grade I–II on MRC (Medical Research Council) scale and retention of urine with normal sensations. Central motor conduction to tibialis anterior (CMCT-TA) on the right side was 32 ms and 24 ms on the left side. Spinal MRI revealed hyperintense signal changes extending from C3 to T12. After 5 days of methylprednisolone therapy, there was marked improvement in weakness, micturition normalized and CMCT-TA also returned to normal. MRI repeated after 1 month was also normal. This response seems to be due to antiedema and to the antiinflammatory effect of methylprednisolone, because of a temporal relationship between MPS and clinical improvement. However, the possibility of natural recovery cannot be ruled out.