A 13-year-old African American male presented with 2 months of subacute altered mental status, ptosis, areflexia, disordered gait, constipation, weight loss, abdominal and testicular pain, and hyperhidrosis. Initial workup at our facility was unrevealing until elevated serum mercury level was detected. Diagnosis of mercury toxicity was confirmed, and chelation therapy with succimer was started. After beginning succimer, the patient developed acute-onset weakness and was diagnosed with acute inflammatory demyelinating polyneuropathy. Supportive studies included elevated cerebrospinal fluid protein and acquired demyelinating polyneuropathy on nerve conduction study. He responded well to treatment with intravenous immunoglobulin and returned to his baseline state of health. Although there is a known association between mercury toxicity and axonal neuropathy, there is only 1 other case report of acute inflammatory demyelinating polyneuropathy in the setting of mercury toxicity. The nature of the correlation between these 2 entities in our case remains unclear.