Abstract: PURPOSE: Accidental death is a leading cause of mortality among military members and Veterans; however, knowledge is limited regarding time-dependent risk following deployment and if there are differences by type of accidental death. METHODS: Longitudinal cohort study (N=860,930) of soldiers returning from Afghanistan/Iraq deployments in fiscal years 2008-2014. Accidental deaths (i.e., motor vehicle accidents [MVA], accidental overdose, other accidental deaths), were identified through 2018. Crude and age-adjusted mortality rates, rate ratios, time-dependent hazard rates and trends postdeployment were compared across demographic and military characteristics. RESULTS: During the postdeployment observation period, over one-third of deaths were accidental; most were MVA (46.0%) or overdoses (37.9%). Across accidental mortality categories (all, MVA, overdose), younger soldiers (18-24, 25-29) were at higher risk compared to older soldiers (40+), and females at lower risk than males. MVA death rates were highest immediately postdeployment, with a significant decreasing hazard rate over time (annual percent change [APC]: -6.5%). Conversely, accidental overdose death rates were lowest immediately following deployment, with a significant increasing hazard rate over time (APC: 9.9%). CONCLUSIONS: Observed divergent trends in risk for the most common types of accidental deaths provide essential information to inform prevention and intervention planning for the immediate postdeployment transition and long-term.