Acute immune-mediated polyneuropathies classified as Guillain-Barre Syndrome (GBS) constitute a wide range of clinical manifestations characterized by ascending symmetrical limbs paralysis along with possible involvement of the respiratory muscles. Paralysis of facial and eye muscles including unresponsive pupils, which may mimic a brain death is rare, though previously described. This presentation is challenging because it masks the correct diagnosis and delays or prevents appropriate treatment. A 69-year-old female patient was hospitalized with progressive bilateral limb paralysis with involvement of the respiratory and facial muscles necessitating intubation. Plasmapheresis resulted in significant motor and respiratory improvement and the patient was sent for further rehabilitation. Six weeks later she was hospitalized again with complete muscle paralysis including involvement of the eye muscles and pupils. In the absence of ocular, corneal, and swallowing reflexes, a working diagnosis of brain death was initially made. However, a repeated and meticulous physical examination revealed that her consciousness was preserved. An EEG test showing brain activity ruled out brain death. EMG showed extensive axonal damage supporting the diagnosis of GBS. Repeated plasmapheresis failed to improve her condition but she had partially responded to treatment with immunoglobulins. Clinicians should be aware of those patients diagnosed as brain dead but who in fact suffer from another treatable disease that needs to be diagnosed.