Although neurological complications have been described after tetanus vaccinations, they are rare. The authors report a case of acute disseminated encephalomyelitis (ADEM) in a 28-year-old pregnant woman at a gestational age of 10 weeks, admitted 15 days after a tetanus vaccination, with spastic tetraplegia and sphincter disturbances. Corticosteroid treatment led to partial recovery of the neurological deficit. Differential diagnosis of infectious and demyelinating diseases of the central nervous system is difficult in view of clinical and laboratory aspects of post-vaccination ADEM. Without any specific diagnostic markers, the clinical examination, magnetic resonance imaging and negative etiological findings were key to this diagnosis. Medical staff must bear in mind the possible complications of this vaccine.