Disaggregated data is a cornerstone of precision health. Vietnamese Americans (VietAms) are the fourth-largest Asian subgroup in the United States (US), and demonstrate a unique burden of disease and mortality. However, most prior studies have aggregated VietAms under the broader Asian American category for analytic purposes. This study examined the leading causes of death among VietAms compared to aggregated Asian Americans and non-Hispanic Whites (NHWs) during the period 2005-2020. Decedent data, including underlying cause of death, were obtained from the National Center for Health Statistics national mortality file from 2005 to 2020. Population denominator estimates were obtained from the American Community Survey one-year population estimates. Outcome measures included proportional mortality, age-adjusted mortality rates per 100,000 (AMR), and annual percent change (APC) in mortality over time. Data were stratified by sex and nativity status. Due to large differences in age structure, we report native- and foreign-born VietAms separately. We identified 74,524 VietAm decedents over the study period (71,305 foreign-born, 3,219 native-born). Among foreign-born VietAms, the three leading causes of death were cancer (26.6%), heart disease (18.0%), and cerebrovascular disease (9.0%). Among native-born VietAms the three leading causes were accidents (19.0%), self-harm (12.0%), and cancer (10.4%). For every leading cause of death, VietAms exhibited lower mortality compared to both aggregated Asians and NHWs. Over the course of the study period, VietAms witnessed an increase in mortality in every leading cause. This effect was mostly driven by foreign-born, male VietAms. While VietAms have lower overall mortality from leading causes of death compared to aggregated Asians and NHWs, these advantages have eroded markedly between 2005 and 2020. These data emphasize the importance of racial disaggregation in the reporting of public health measures.