A case of delayed myelopathy appearing 15 years after a stab wound to the thoracic spine with a retained foreign body in the spinal canal is reported. Severe inflammatory reaction to iron corrosion was found, with granuloma and sterile pus formation. Removal of the foreign body and partial excision of the granuloma resulted in clinical improvement. Reaction to foreign body corrosion is believed to be the major cause of delayed neurologic deficit and is an important guideline for removal of asymptomatic intraspinal foreign bodies.