Spinal intramedullary teratoma is a rare tumor. We report a case of intramedullary teratoma of the conus medullaris with spina bifida. A 5-year-old boy was admitted to our hospital for removal of a lumbosacral tumor sited in an intramedullary location at the conus medullaris, which was totally resected with neuroendoscopic assistance. The pathological diagnosis was mature teratoma consisting of three germ cell layers. The pathogenesis of spinal intramedullary teratoma is discussed with special reference to spina bifida.