The presence of alcohol is clearly a risk factor for sustaining a traumatic brain injury (TBI); however, the impact of alcohol on injury severity, and functional or cognitive outcome is unclear, as there is mixed evidence in the literature. This study examined 482 participants in a large urban medical center with documented mild-complicated to severe TBI and blood alcohol testing for functional and cognitive outcome. Functional outcomes were measured by the Functional Independence Measure (FIM) and cognitive outcomes were measured using neuropsychological tests known to be sensitive to the sequelae of TBI. Consistent with the hypotheses, there was a statistically significant negative impact of alcohol intoxication at the time of injury on Glasgow Coma Scale (GCS); however intoxication only lowered GCS by an average of 1.9 points. There was a statistically significant relationship between blood alcohol levels (BAL) and FIM at the time of admission to inpatient rehabilitation, but BAL accounted for only 3% of the variance in FIM total score. There was no relationship between BAL and FIM at discharge from rehabilitation or at 1-year follow-up. There was no statistically significant relationship between BAL at the time of injury and cognitive functioning at 1-year follow-up; however, contrary to the hypotheses GCS failed to show a strong relationship with cognitive outcome.