We report a case involving a 7-year-old girl who initially presented with seizure and hypertensive encephalopathy, serious autonomic manifestations associated with Guillain-Barré syndrome, followed by subsequent bilateral ascending flaccid paralysis. Cerebrospinal fluid analysis showed cytoalbuminous dissociation. Nerve conduction velocity tests showed features of demyelinating polyradiculoneuropathy. An immunofluorescence test of her serum was positive for mycoplasma immunoglobulin M antibody. The present case highlights the importance of considering the initial autonomic manifestations of Guillain-Barré syndrome in the differential diagnosis of unexplained acute hypertensive crisis.