A 34-week floppy preterm infant born to a mother with acute ulcerative colitis presented with a progressive reduction in spontaneous limb movements, severe generalized hypotonia, areflexia, autonomic dysfunction and respiratory failure. Electromyography revealed pronounced denervation activity and markedly slow nerve conduction velocity (3 m/s) with evidence of conduction block. These findings indicated demyelination with additional axonal features. The infant was diagnosed with congenital Guillain-Barré syndrome, was treated with intravenous immunoglobulin and showed clinical improvement within 48 hours of treatment. The relationship between inflammatory bowel syndrome and inflammatory demyelinating polyneuropathy is discussed.