Objectives: We report on a patient presenting with an isolated polyneuropathy mimicking Guillain-Barré syndrome (GBS) associated with arsenic exposure. Case: A 43-year-old man visited our emergency room complaining of progressive quadriparesis over the prior 5 days. His clinical course with laboratory data was typical of GBS. However, because of his recent use of herbal medication, we screened for the presence of several heavy metals. Serial analyses of urinary inorganic arsenic concentrations confirmed exposure to arsenic. He was diagnosed as arsenic neuropathy mimicking GBS without any systemic manifestation of arsenic intoxication. Conclusions: The present case study emphasizes the need to consider arsenic intoxication in patients presenting with acute demyelinating neuropathies and histories of herbal medication use.