Background: Ventral cord herniation from dura defect is a rare cause of progressive myelopathy due to the thoracic cord herniation through the dural defect. Most of cases are congenital or idiopathic, while some patients with history of previous trauma or surgery in the thoracic region. The dura defect usually need repair to prevent the progression of neurological deficit. Case report: A 33-year-old man presented with an insidious onset and progressive numbness over right lower chest for about 2 years. He had a history of traffic accident and underwent a repair of right knee tendon rupture 4 years before. In the past two years, He also experienced intermittent mild to severe upper back pain, sometimes radiating to the neck. The pain was aggravated by cough and on raising up from bed suddenly. He got a scald burn over right calf due to a reduction of thermal sensation on his right lower leg. The neurological examination revealed right leg weakness with muscle strength of 4/5 and reduced pain and temperature sensation below right chest (about T5 level). The vibration was also decreased on right lower limb. The spinal magnetic resonance imaging study showed a dura ventral herniation of spinal cord at the T3,4 level. Due to the progressive sensory symptoms of thoracic myelopathy, he underwent an operation of total laminectomy of T2-5 with repair of ventral dura defect. After the surgical treatment, his back pain relieved and the numbness ameliorated as well. Conclusion: Symptomatic myelopathy is usually caused by compression from degenerative disease, tumor, injury, circulatory or inflammatory diseases, idiopathic ventral spinal cord herniation is a rare cause of thoracic myelopathy. Most patients experience progressive myelopathy for many years before the exact diagnosis is achieved. Early diagnosis by neuroimage is essential to prevent irreversible neurological dysfunction.