Objective To assess knowledge of nurses of emergency services and intensive care units about Glasgow Coma Scale.Methods This cross-sectional analytical study included 127 nurses of critical units of an university hospital. We used structured interview with 12 questions to evaluate their knowledge about the scale. Association of Knowledge with professionals’ sociodemographic variables were verified by the Fisher-test, χ2 and likelihood ratio.Results Most of participants were women mean aged 31.1 years, they had graduated more than 5 years previously, and had 1 to 3 years of work experience. In the assessment of best score possible for Glasgow scale (question 3) nurses who had graduate more than 5 years ago presented a lower percentage success rate (p=0.0476). However, in the question 7, which evaluated what interval of the scale indicated moderate severity of brain trauma injury, those with more years of experience had higher percentage of correct answers (p=0.0251). In addition, nurses from emergency service had more correct answers than nurses from intensive care unit (p=0.0143) in the same question. Nurses graduated for more than 5 years ago had a lower percentage of correct answers in question 7 (p=0.0161). Nurses with more work experience had a better score (p=0.0119) to identify how assessment of motor response should be started.Conclusion Number of year since graduation, experience, and work at critical care units interfered in nurses’ knowledge about the scale, which indicates the need of training.