BackgroundThe assessment of pupil size and reaction to light is a fundamental part of the neurological assessment; however, manual examination is prone to inaccuracies. The use of an automated infrared pupillometer is one strategy to limit error in pupil examination. ObjectiveThe main objective was to assess agreement between manual examination and examination using an automated infrared pupillometer in relation to pupil reaction and size in a specialised neurosciences intensive care unit. MethodsWe conducted a single-centre prospective observational study in a specialised tertiary neurosciences intensive care unit. Participants' pupils were examined hourly for 24 h by both manual examination using a pen torch and examination using an automated infrared pupillometer. ResultsTwenty-two participants were enrolled. A total of 935 paired pupil observations were obtained for both pupil reaction and size. There was no statistically significant disagreement in assessing pupil reaction (McNemar's test p = 0.106). Percentage agreement was 96.68% for pupil reaction, with Kappa coefficient, 0.841 (95% confidence interval: 0.7864–0.8956). For all participants, the mean difference in pupil size was 0.154 mm, with limits of agreement of −1.294 mm to +1.603 mm. ConclusionThere was no significant disagreement between manual and automated pupillometer observations for pupil reaction. The mean difference in measurement of pupil size was small.