Treatment of high-grade dysplastic spondylolisthesis in adolescents remains challenging. Surgical treatment of spondylolisthesis has been recommended in adolescents with pain refractory to conservative treatment, slippage progression, or severe slippage on presentation. Controversy exists as to the optimal surgical approach for high-grade spondylolisthesis. Moreover, some authors reported the incidence of L5 root palsy during the reduction procedure. We performed 2 cases of surgical treatment using intraoperative electrophysiological monitoring for patients with high-grade dysplastic spondylolisthesis in adolescence. Each patient received treatment consisting of decompression of nerve with surgical microscope, reduction, and circumferential fusion with transpedicular and monosegmental fixation surgery with intraoperative neurological monitoring with transcranial electric motor evoked potentials and continuous spontaneous electromyography recording. Intraoperative monitoring did not show any abnormal changes. The patients got well after surgery, and they showed no postoperative motor paralysis of the extremities. A postoperative radiogram showed reduction of the slippage, and computed tomogram showed bone union between L5 and S1 vertebral body. This report describes 2 cases of surgical treatment using intraoperative electrophysiological monitoring with transcranial electric motor evoked potentials and continuous spontaneous electromyography for patients with high-grade dysplastic spondylolisthesis in adolescence. We successfully perform the surgery without any neurological deficit using intraoperative electrophysiological monitoring.