Background: Hyperglycemia is frequently encountered in critically ill patients and has been shown to contribute to both morbidity and mortality. We aimed to study the predictive role of blood glucose level in clinical outcomes of mechanically ventilated patients with traumatic brain injury during intensive care unit (ICU) stay and to explore its relationship with Glasgow coma scale (GCS) and acute physiology and chronic health examination (APACHE) II scores that are used in the evaluation of ICU patients as predictor. Materials and Methods: A total of 185 patients with craniocerebral trauma who were hospitalized in the ICU were included in the study. Comparisons of mean glucose values (MGVs) and APACHE II scores between survivors and nonsurvivors were made with Student's t-test and chi-square test. Survival analysis was performed with log rank (Mantel-Cox) test and Cox regression was used for mortality risk factors analysis. Results: MGVs at the initial, last, and all measurements were significantly higher for nonsurvivors than for survivors. Hazard rate at any given time point for patients with mean glucose value (MGV) between 150 and 179 was found to be 3.691 times that of patients with MGV values between 110 and 149. The hazard rate at any given time point for patients with MGV values >= 180 was found to be 6.571 times that of patients with MGV values between 110 and 149. Conclusion: High glucose level is an independent risk factor for mortality in mechanically ventilated ICU patients with traumatic brain injury.