Posterior epidural migration (PEM) of free disc fragments is rare, and reported PEM patients usually presented with radicular signs. An uncommon case involving a patient with cauda equina syndrome due to PEM of a lumbar disc fragment is reported with a review of the literature. The patient described in this report presented with an acute cauda equina syndrome resulting from disc fragment migration at the L3-L4 level that occurred after traction therapy for his lower back pain. The radiological characteristics of the disc fragment were the posterior epidural location and the ring enhancement. A fenestration was performed and histologically confirmed sequestered disc material was removed. An early postoperative examination revealed that motor, sensory, urological, and sexual functions had been recovered. At late followup, the patient was doing well after 18 months. Sequestered disc fragments may occasionally migrate to the posterior epidural space of the dural sac. Definite diagnosis of posteriorly located disc fragments is difficult because the radiological images of disc fragments may mimic those of other more common posterior epidural lesions.