Objective: To quantify and describe excess mortality attributable to traumatic brain injury (TBI) during the 12 months after hospitalization. Design: Population-based matched cohort study using linked hospital and mortality data. Setting: Australia. Participants: Individuals 18 years and older who were hospitalized with a principal diagnosis of TBI in 2009 (n = 6929) and matched noninjured individuals randomly selected from the electoral roll (n = 6929). Main Measures: Survival distributions were compared using a Kaplan-Meier plot with a log-rank test. Mortality rate ratios (MRRs) were computed using Cox proportional hazard regression with and without controlling for demographic characteristics and preexisting health status. Results: Individuals with TBI experienced significantly worse survival during the 12 months after hospitalization (χ2 = 640.9, df = 1, P < .001), and were more than 7.5 times more likely to die compared with their noninjured counterparts (adjusted MRR, 7.76; 95% confidence interval, 6.07–9.93). TBI was likely to be a contributory factor in 87% of deaths in the TBI cohort. Excess mortality was higher among males, younger age groups, and those with more severe TBI. Conclusion: Excess mortality is high among individuals hospitalized with TBI and most deaths are attributable to the TBI. Increased primary and secondary preventive efforts are warranted to reduce the mortality burden of TBI.