We report a case of acute myelitis associated with hepatitis C virus (HCV) infection. A Japanese woman developed left calf pain and weakness, but this quickly generalised to paraplegia. We diagnosed acute myelitis based on the results of clinical manifestations, an MRI examination and a cerebrospinal fluid (CSF) examination. The clinical condition and spinal cord lesions improved following intravenous administration of methylprednisolone. The patient had been diagnosed with HCV infection 11 years before the onset. We detected HCV RNA in the CSF, supporting the strong association of our patient's myelitis. However, it is difficult to conclude whether the neurological condition was caused directly by the viral load or indirectly by the immune response. We suggest that testing for HCV infection is important in patients with myelitis. In particular, anti-HCV antibody and HCV RNA should be measured in the patients' serum as well as CSF.