Dural ectasia refers to the widening or ballooning of the dural sac surrounding the spinal cord. It can affect any plane of the spinal canal, but occurs primarily in the lumbosacral region. Dural ectasia is present in 63-92% patients who have Marfan syndrome, and is related to Ehlers-Danlos syndrome, neurofibromatosis type I, and ankylosing spondylitis. The most common symptoms are low back pain, headache, weakness, numbness above and below the affected limb, and occasional rectal and genital pain. However, in most patients, dural ectasia is usually asymptomatic. We report the case of a 5-year-old boy who presented with a severe headache who had been diagnosed with Marfan syndrome. During the evaluation, magnetic resonance imaging of the lumbar and sacral spine revealed dural ectasia. To our knowledge, this is the first report on Marfan syndrome with symptomatic dural ectasia in Korea. We concluded that dural ectasia should be suspected in patients diagnosed with Marfan syndrome who have a severe headache.