Patients with ankylosing spondylitis (AS) are prone to spinal fracture after even minor trauma. We report a case of thoracic spinal fracture in a patient with AS who developed a secondary neurological deficit due to delayed diagnosis and prolonged conservative treatment. When the neurological deficit occurred, the fractured segment showed no displacement, but a spinal epidural hematoma was present. Surgical treatment produced significant neurological improvement, although incomplete paralysis persisted.