INTRODUCTION: Post-infectious autoimmune demyelination of the central nervous system is a rare neurological disorder typically associated with exanthematous viral infections. We report an unusual presentation of the condition and a previously undocumented association with Streptococcus pneumonia meningitis. CASE PRESENTATION: A 50-year-old Caucasian woman presented to our facility with an acute myelopathy three days after discharge following acute Streptococcus pneumoniae meningitis. Imaging studies of the spine ruled out an infective focus and no other lesions were seen within the cord. Diffuse, bilateral white matter lesions were seen within the cerebral hemispheres, and our patient was diagnosed as having a post-infective demyelination syndrome that met the diagnostic criteria for an acute transverse myelitis. Our patient clinically and radiologically improved following treatment with steroids. CONCLUSIONS: The novel association of a Streptococcus pneumoniae infection with post-infectious autoimmune central nervous system demyelination should alert the reader to the potentially causative role of this common organism, and gives insights into the pathogenesis. The unusual dissociation between the clinical presentation and the location of the radiological lesions should also highlight the potential for the condition to mimic the presentation of others, and stimulates debate on the definitions of acute transverse myelitis and acute disseminated encephalomyelitis, and their potential overlap.