We report a 35-year-old man who developed weakness in his extremities five months after pegylated interferon α (IFNα)-2b was administered. The serum tumor necrosis factor-α (TNFα) was elevated and nerve conduction studies revealed demyelination both in the distal and intermediate segments. The sural nerve pathology showed mild demyelinating process. The cessation of IFNα and administration of intravenous immunoglobulin improved both his clinical symptoms and the temporal dispersion in motor nerve conduction study. IFNα-induced CIDP is presumably a transient immunological condition that requires immunomodulatory therapy. The elevated serum TNFα may implicate the degree of downstream autoimmunity induced by IFNα.