There has been no gold standard for intraoperative monitoring in carotid endarterectomy (CEA) till now. The purpose of the current study was to investigate the value of near-infrared spectroscopy (NIRS) monitoring in CEA and explore the thresholds for intraoperative cerebral hypoperfusion. Eighty-four consecutive patients who underwent CEA surgery in Xuan Wu Hospital of Capital Medical University from August 2015 to June 2016 were enrolled in this study. All patients were intraoperatively monitored by transcranial Doppler ultrasonography (TCD) and NIRS. Regional oxygen saturation (rSO(2)) monitored by NIRS and blood flow velocity of the middle cerebral artery (V-MCA) monitored by TCD were continuously recorded. Correlation analysis was conducted for NIRS and TCD monitoring values. Intraoperative shunting was performed in five patients according to the TCD monitoring results and surgeon preference. During clamping of the carotid artery, the Pearson correlation index between rSO(2) and V-MCA was 0.581 (P<0.001). A cut-off of 12.3% decrease of rSO(2) was identified as the optimal threshold for intraoperative hypoperfusion indicated by TCD monitoring, when the sensitivity and specificity were 74.6% and 91.7%, respectively, with a 0.609 Kappa value. Physical examination immediately after operation showed no ischemic injury occurred, and no death and stroke occurred during the postoperative hospitalization. Our study demonstrated that NIRS could serve as a favorable monitoring tool during CEA. A 12.3% decrease of rSO(2) could be adopted as a reliable threshold for intraoperative cerebral hypoperfusion.