We report a female patient with posterior reversible encephalopathy syndrome as the initial manifestation of a Guillain-Barré syndrome. She presented with headache and paraesthesias of the fingertips three days after gastroenteritis. Examination revealed hypertension and tachypnoea. Brain MRI showed a bi-occipital vasogenic edema consistent with the syndrome. Subsequent examination showed a tetraparesis. Cerebrospinal fluid analyses revealed albuminocytologic dissociation and the diagnosis of Guillain-Barré syndrome was made. The typical radiological and clinical features of posterior reversible encephalopathy syndrome (headache and hypertension) were present prior to the clinical manifestation of Guillain-Barré syndrome. We suggest posterior reversible encephalopathy syndrome to be considered as an initial manifestation of Guillain-Barré syndrome.