The objective of this study was to describe an adult male patient with ankylosing spondylitis (AS) associated with thoracic spinal cord herniation (TSCH).TSCH is a scarce entity presented as a displacement of thoracic cord through an anterior or anterolateral dural defect.More importantly, the co-occurrence of AS and thoracic spinal cord herniation is exceptional.To date, only one case of SCH in association with AS has been reported in the literature.A 56-year-old male patient presented with the progressive difficulty in walking and numbness of both lower limbs for the past 18 months.The patient was diagnosed as AS when he was 30 years old.Sagittal MRI of thoracic spine showed dural defect of the posterior aspect of T11 and 12 vertebral bodies.Axial T2-weighted MRI demonstrated that spinal cord was displaced ventrally and to the right.The diagnosis of TSCH with AS was established.The prognosis was explained to the patient.We recommended duraplasty for dural repair to the patient, but he refused surgery.The results demonstrated that TSCH associated with long-standing AS was very uncommon, and MRI is recommended to rule out SCH in the long-standing AS patients with neurologic symptoms.The SCH in AS might be caused by inflammation, and thoracolumbar hyperkyphosis results from AS might be associated with the development of SCH.