Many Mycoplasma pneumoniae extra respiratory infections have already been reported. The authors report the case of an eight year old child, presenting with acute transverse myelitis, with a PCR proven involvement of M. pneumoniae in CSF as well as the presence of specific IgM in blood. Acute transverse myelitis may have many causes, most of the time viral. The mechanisms of neurological involvement in M. pneumoniae infections are still unclear, but several points indicate an immune reaction. Corticotherapy first i.v. then per os has proved to be an efficient treatment for acute myelitis. Antibiotherapy is discussed because of the undocumented mechanisms of neurological involvement related to the mycoplasma.