Objective To examine a) ethnic differences in blood alcohol level (BAL) and pre-injury chronic alcohol use (PI-ETOH) within a severe closed head injury (CHI) sample, and b) the main and interaction effects of BAL, PI-ETOH, and ethnicity on functional outcome following severe CHI. Participants 434 Hispanic, Anglo-Caucasian, and African American individuals with severe CHI. Design Retrospective cohort study. Setting Consecutive admissions to a level one trauma center. Main measures BAL upon admission to the trauma center was collected for each patient. Additional information regarding PI-ETOH was collected in a subset of patients (N=116). Functional outcome was measured using the Disability Rating Scale (DRS) at 6 months post-injury. Results A one-way ANOVA revealed ethnic differences in mean BAL. Hierarchical multiple regression indicated that BAL did not predict DRS outcomes after controlling for pertinent covariates. An interaction effect between PI-ETOH and ethnicity was observed, such that presence of chronic alcohol use predicted worse functional outcome for Anglo-Caucasians and African Americans, but more favorable outcome for Hispanics. Conclusions Ethnic differences in BALs within our severe TBI sample mirrored ethnic drinking patterns observed in the general population, with Hispanics having the highest BALs. A paradoxical relationship between PI-ETOH and functional outcome was observed for Hispanics.