Background/Aims: This study aims to compare the reliability of the Full Outline of Unresponsiveness (FOUR) score and the Glasgow Coma Score (GCS) when used by specialists from different medical disciplines. Methods: This prospective observational study was conducted at Selçuk University Faculty of Medicine between December 2023 and June 2024. Eighty-two patients in the Anesthesiology and Reanimation Intensive Care Unit (ICU) were assessed by three specialists—the pulmonologist, the neurologist, and the anesthesiologist—within 24 hours of ICU admission. The scores for each patient by each specialist independently were recorded within a time interval of one hour, consecutively, as possible to minimize the likelihood of any changes in the patient’s condition. The variation between evaluators of both scoring systems was analyzed using the Intraclass Correlation Coefficient (ICC). If ICC was below 0.50, the agreement was interpreted as poor. Results: The study included 82 patients. There were no statistically significant differences in the FOUR and GCS scores assigned by the three specialists. The mortality rate among patients with low scores on both FOUR and GCS was higher than the hospital mortality rate. Conclusions: Scales used in the ICU should be simple, reliable, and predictive. This study demonstrated that the FOUR is at minimum equivalent to the GCS in meeting these criteria.