Abstract: OBJECTIVES: The association between traumatic brain injury (TBI) and alcohol use disorder (AUD) is known, but the extent of TBI's role in developing AUD remains unclear. This study examines the association between TBI severity with subsequent AUD diagnosis, and hazard for death due to alcohol, drug overdose, or suicide. METHODS: Data from a national US military/veteran cohort (October 1999-September 2016, followed until September 2020) were analyzed using Fine-Gray competing risk models to investigate the relationships between TBI exposure, subsequent AUD, and hazards of death due to specific causes (alcohol, drug overdose, or suicide). RESULTS: TBI severity correlated with an increased likelihood of an incident AUD diagnosis: mild TBI (hazard ratio [HR]: 1.25, 95% confidence interval [CI] 1.22-1.27), moderate-severe TBI (HR: 1.34, 95% CI 1.32-1.37), and penetrating TBI (HR: 1.90, 95% CI 1.86-1.94). For those who developed AUD, TBI was associated with a higher hazard of death from specific causes such as alcohol, drug overdose, or suicide (HR: 2.47 (95% CI 2.03-3.02) for mild TBI, 4.25 (95% CI 3.49-5.17) for moderate-severe TBI, and 3.39 (95% CI 2.80-4.13) for penetrating TBI. CONCLUSIONS: Veterans with TBI were more likely to develop AUD and experience increased mortality, even after adjusting for demographic and clinical factors. Care strategies that are sensitive to the cognitive and/or emotional impairments associated with varying levels of TBI may lead to better outcomes, reducing both AUD and mortality rates. Further research is needed to develop evidence-based methods for integrating TBI and AUD care.