Objective To assess the application safety, feasibility, and measurement performance of a near-infrared system that monitors pupil size through closed eyelids in neurosurgical patients. Methods We prospectively enrolled 30 awake neurosurgical patients in this prospective validation study.Manual pupil measurements obtained with the eyes open were used as the clinical reference standard.We assessed the safety and feasibility of the closed-eye pupil monitoring system and evaluated its measurement accuracy using mean absolute error, root mean square error, and Bland-Altman analysis. Results In the safety validation study, no device-related adverse events or physical safety incidents were recorded at either follow-up assessment, conducted within 10 minutes of device removal (T1) and within 72 hours (T2).Compared with the manual reference measurements obtained with the eyes open, the automated closed-eye measurements had a mean absolute error of 0.14 mm and a root mean square error of 0.16 mm.Bland-Altman analysis showed a mean bias of -0.10 mm, with 95% limits of agreement ranging from -0.36 to 0.15 mm. Conclusion Application of the near-infrared closed-eye pupil monitoring system in awake neurosurgical inpatients is safe and feasible, and it exhibits reliable measurement performance.