The purpose of this study was to examine independent risk factors, and in particular the impact of alcohol on the development of delirium, in a cohort of trauma patients screened for ethanol ingestion on admission to hospital. The National Trauma Databank (v. 7.0) was used to identify all patients 18 years or older screened for ethanol on admission. Patients who developed delirium were compared with those who did not. Stepwise logistic regression analysis was used to identify independent risk factors for the development of delirium. A total of 504,839 patients with admission ethanol levels were identified. Of those, 2,909 (0.6%) developed delirium. Patients developing delirium were significantly older, more frequently male, and more likely to sustain thermal injuries and falls. Patients developing delirium had more comorbidities including chronic ethanol use (19.1% vs. 4.5%, P < 0.001) and cardiovascular disease (21.5% vs. 12.2%, P < 0.001). On admission, patients developing delirium were more likely to be intoxicated with ethanol (55.4% vs. 26.5%, P < 0.001) and were more likely to be uninsured (17.8% vs. 0.9%, P < 0.001). A stepwise logistic regression model identified lack of insurance, positive ethanol on admission, chronic ethanol use, Intensive Care Unit admission, age ≥ 55 years, burns, Medicare insurance, falls, and history of cardiovascular disease as independent risk factors for the development of delirium. The incidence of delirium in this trauma patient cohort was 0.6 per cent. The above risk factors were independently associated with the development of delirium. This data may be helpful in designing interventions to prevent delirium.