Rugby performance features repeated head impacts in both training and competition. Such head impacts are related to brain disease and cognitive deficits with females being potentially more at risk than males (Allan et al., 2024). There is no currently accepted field-based method of monitoring effects of potential brain injuries in the absence of diagnosable concussion. Automated measurement of the pupillary light reflex (PLR) has been proposed as a solution to this issue (Kirk & Childs, 2023) but data are lacking for rugby performance. An adult mixed sex cohort (male n=44 ; female n=68) participated in this study following institutional ethical approval. PLR of both eyes were measured in ambient indoor light (270-330 Lux) pre and post competitive rugby matches using Neuroptics NPi-200 automated pupilometer (Irvine, USA). Variables measured were min and max pupil diameter (mm), peak constriction velocity (CV, mm∙s^-1), mean CV (MCV, mm∙s^-1), dilation velocity (DV, mm∙s^-1), amplitude (%), latency (s) and ‘NPi’ (AU) – a proprietary variable representing overall pupil response. Two-way repeated measures ANOVAs were calculated for all variables using Bayes factors (BF₁₀) ≥3 as inference and post hoc analyses with Cohen’s d effect size (JASP 0.95.3). NPi displayed decisive pre-post reductions (BF₁₀ = 5.407⁺¹²) with females reducing more (BF₁₀ = 8.7, d = .84). Max diameter (BF₁₀ = 1.206⁺⁶, d = .36 increase), min diameter (BF₁₀ = 4.799⁺¹⁰, d = .59 increase), amplitude (BF₁₀ = 1.059⁺⁷, d = .55 decrease) and DV (BF₁₀ = 5,529, d = .39 decrease) all showed decisive pre-post changes but no differences between sexes. Females displayed differences in both CV (BF₁₀ = 4.2, d = .37 decrease) and MCV (BF₁₀ = 15.8, d = .44 decrease) compared to males, but only MCV had pre-post differences (BF₁₀ = 34.3, d = .21). Latency had very strong pre-post increases (BF₁₀=99, d=.35 increase), without differences between sexes. Both sexes showed increased pupil diameter following rugby performance, possibly related to arousal. Pupils in both sexes were slower to respond and responded less to stimulus post-performance, which may be related to head impacts. Changes in CV only occurred in females, suggesting females may be more affected by head impacts during rugby performance than males. These data support the potential use of PLR in monitoring brain function in competitive sports environments.