Importance: Atherosclerotic cardiovascular disease (ASCVD) remains a leading cause of death and disability in the US and worldwide. Influenza vaccination has shown to decrease overall morbidity, mortality, severity of infection, and hospital readmissions among these individuals. However, national estimates of influenza vaccination among individuals with ASCVD in the US are not well studied. Objective: To evaluate the prevalence of and sociodemographic disparities in influenza vaccination among a nationally representative sample of individuals with ASCVD. Design, Setting, and Participants: Pooled Medical Expenditure Panel Survey data from 2008 to 2016 were used and included adults 40 years or older with ASCVD. Participants' ASCVD status was ascertained via self-report and/or International Classification of Diseases, Ninth Revision diagnosis of coronary heart disease, peripheral artery disease, and/or cerebrovascular disease. Analysis began April 2020. Main Outcomes and Measures: Prevalence and characteristics of adults with ASCVD who lacked influenza vaccination during the past year. Covariates including age, sex, race/ethnicity, family income, insurance status, education level, and usual source of care were assessed. Results: Of 131881 adults, 19793 (15.7%) had ASCVD, corresponding to 22.8 million US adults annually. A total of 7028 adults with ASCVD (32.7%), representing 7.4 million adults, lacked influenza vaccination. The highest odds of lacking vaccination were observed among individuals aged 40 to 64 years (odds ratio [OR], 2.32; 95% CI, 2.06-2.62), without a usual source of care (OR, 2.00; 95% CI, 1.71-2.33), without insurance (OR, 2.05; 95% CI, 1.63-2.58), with a lower education level (OR, 1. 25; 95% CI, 1.12-1.40), with a lower income level (OR, 1.14; 95% CI, 1.01-1.27), and of non-Hispanic Black race/ethnicity (OR, 1.24, 95% CI, 1.10-1.41). A stepwise increase was found in the prevalence and odds of lacking influenza vaccination among individuals with increase in high-risk characteristics. Overall, 1171 individuals (59.7%; 95% CI, 55.8%-63.5%) with 4 or more high-risk characteristics and ASCVD (representing 732524 US adults annually) reported lack of influenza vaccination (OR, 6.06; 95% CI, 4.88-7.53). Conclusion and Relevance: Despite current recommendations, a large proportion of US adults with established ASCVD lack influenza vaccination, with several sociodemographic subgroups having greater risk. Focused public health initiatives are needed to increase access to influenza vaccinations for high-risk and underserved populations..