Background: A simple arithmetic combination of the Glasgow Coma Scale (GCS) score and pupillary response, the GCS-Pupil (GCS-P), extends the information provided about the patient outcome to an extent comparable to that obtained using more complex methods. The objective of the study was to compare the changes in the GCS-P score of patients with traumatic brain injury (TBI) under alcohol intoxication and nontoxication over time. Methods: A prospective observational study was done in a hospital at the Level I trauma center. The patients admitted to the emergency department (ED) with TBI were the study participants. They were grouped into intoxicated and nonintoxicated based on blood alcohol concentration (BAC). BAC of 0.08% and above was considered intoxication. GCS-P score in the ED and the best day 1 GCS-P score were the outcome variables. For nonnormally distributed quantitative parameters, medians and interquartile range were compared between study groups using Mann−Whitney U-test. P <0.05 was considered statistically significant. Results: A total of 216 patients were included in the final analysis. There was no statistically significant difference between BAC in GCS-P score at different follow-up periods, GCS-P score (ED), and GCS-P score (best day 1). Conclusion: This prospective observational study showed a low GCS-P score for alcohol-intoxicated patients compared to nonintoxicated patients, which was not statistically significant. There was no significant difference in emergency GCS-P score and best day 1 score between alcohol-intoxicated and nonintoxicated patients.