Introduction: Although alcohol use increases the risk of experiencing a traumatic brain injury (TBI), it remains unclear whether outcomes in alcohol-impaired patients are different from those of unimpaired patients. The objective of this study was to evaluate the effect of alcohol on length of stay (LOS) and mortality in patients with major TBI. Methods: Using data collected from the Nova Scotia Trauma Registry, we performed a retrospective analysis of all patients with major TBI (defined as having an abbreviated injury score (AIS) head ≥3) seen in Nova Scotia hospitals between 2002 and 2013. Patients were compared by blood alcohol concentration (BAC) at time of injury: negative (0-1.9 mmol/L), low (2-21 mmol/L), and moderate/high (≥22 mmol/L). A logistic regression model was constructed to test for outcomes and adjusted for the effects of age, gender, location, injury severity score (ISS), and BAC level. Results: In a twelve-year period, there were 4152 major TBI patients in Nova Scotia. Alcohol testing was performed in 43% of cases (80% male, mean age 44±20 years), with 48% having a positive BAC. Mean acute LOS was similar for all three BAC groups. Increasing age (odds ratio [OR]=1.01; p<0.001), high ISS (OR=4.92; p<0.001), injuries occurring outside of Halifax Regional Municipality (OR=1.72; p<0.001), and having a lower BAC level (OR = 0.99; p<0.001) independently predicted mortality. Conclusion: Our findings suggest that low BAC levels are associated with increased mortality in major TBI patients. Further study is warranted to elucidate alcohol’s mechanism in TBI outcomes.