We report a rare case of extensive extradural teratoma successfully treated by multi-stage laminotomy and thoracotomy. A 34-day-old, dyspneic infant had a large posterior mediastinal mass identified on a chest X-ray radiograph. Imaging studies disclosed that the mass originated from the extradural space at the level of the lower thoracic spine, extending cephalad to C4 and caudad to L4 and severely compressing the spinal cord anteriorly, causing paraplegia. The tumor expanded bilaterally through the intraspinal foramina, coalescing to form a huge mediastinal mass. The upper half of the teratoma was removed utilizing a laminotomy from T3 through T9; 2 months later the lower half was excised via a laminotomy from T11 to L3. An additional procedure was required to resect recurrent tumor through a laminotomy from T8 to T12. The reconstructed vertebral arches were well-preserved in shape, with an almost normal spinal canal.