In this report, we described an adult case with a lumbar herniated nucleus pulposus that had migrated to the S1 nerve root foramen from L5-S1 disc space. Endoscopically, the migrated mass was successfully removed after laminectomy at the S1 with a small skin incision of 20 mm in length. Unlike the other levels, the intraforaminally migrated mass along the S1 root can be excised without any removal of the facet joints; therefore, additional spinal fusion is not necessary. Thus, an S1 foraminal migrated mass can be a good surgical candidate for minimally invasive endoscopic surgery.