BACKGROUND: A change in the pupillary light reflex (PLR) is a sensitive indicator for detecting expanding intracranial lesions. Changes in PLR may be a prognostic marker for patients with intracranial lesions. The purpose of this analysis was to explore how PLR readings, size, constriction velocity (CV), dilation velocity (DV), Neurologic Pupil Index (NPi), and latency predict clinical outcome in patients with subarachnoid hemorrhage. METHODS: This is a secondary analysis of prospectively collected multicenter registry data. The within-subject standard deviation (WSD) of PLR values, NPi, size, CV, DV, and latency were explored as predictors of discharge modified Rankin Scale (mRS) in patients with subarachnoid hemorrhagic. RESULTS: Among 4403 pupillary readings from 82 patients with a diagnosis of subarachnoid hemorrhage, with a mean age of 57.7 years, the admission Glasgow Coma Scale median score was 14 (eye, 4; verbal, 4; motor, 6), and the mRS median was 0 on admission and 4 at discharge. Correlation between standard deviation of PLR values and discharge mRS was moderate and negative (r = −0.3 to −0.47, P < .01). The standard deviations for NPi, size, CV, and DV were significant for predicting discharge mRS (r2 = 0.23–0.28, P < .05) after controlling for admission Glasgow Coma Scale. CONCLUSION: Patients with higher WSD PLR values showed better outcomes (ie, lower mRS at discharge), suggesting that patients with narrower WSD PLR are at a higher risk for poor outcomes.