Introduction: Healthy diet perception may influence cardiovascular (CV) outcomes. Misperceptions on the healthfulness of one’s diet can interfere with the precontemplative and contemplative stages of behavioral change if individuals overestimate their diet quality. Using a nationally-representative sample, we explored the prevalence of healthy diet misperception in the general population and in those with CV diseases, as well as whether misperceptions are associated with clinical CV risk factors. Methods: We included adults≥20 years old from the National Health and Nutrition Examination Survey 2017-2020. Using survey data on participants’ perception of their own diet and diet recall data to calculate Healthy Eating Index-2015 (HEI), we divided participants into dietary quantiles. We categorized healthy diet perception (HDP) as overestimated (perceived>HEI quantile), accurate (perceived=HEI quantile), or underestimated (perceived<HEI quantile). We categorized those who self-reported hypertension, coronary heart disease, myocardial infarction, congestive heart failure, and stroke as having CV disease. Clinical CV risk factor measures were body mass index (BMI), systolic blood pressure (SBP), diastolic blood pressure (DBP), hemoglobin A1c, total cholesterol, low-density lipoprotein (LDL), and high-density lipoprotein (HDL). We used multiple logistic regression to measure the association between CV disease and HDP and multiple linear regression for HDP and CV risk factors, stratified by presence of CV disease. Results: Of 7,710 adults, 4,470 (57.5 weighted %) overestimated HDP; 1,924 (25.6 weighted %) underestimated HDP; and 1,316 (16.9 weighted %) correctly estimated HDP. After adjusting for age, sex, and education level, having CV disease was not associated with incorrectly estimating HDP (adjusted OR 1.08; 95% CI 0.93, 1.26) or overestimating HDP (adjusted OR 1.21; 95% CI 1.00, 1.48), compared to correctly estimating HDP. Among those with CV disease, overestimating HDP was associated with higher BMI (adjusted difference 1.9 m/kg 2 ; 95% CI 0.8, 2.9) and lower HDL (adjusted difference -2.8 mg/dL; 95% CI -5.1, -0.5). Among those without CV disease, overestimating HDP was only associated with higher BMI (adjusted difference 1.9; 95% CI 0.8, 2.9) Conclusions: More than half of Americans overestimate their diet quality, and adults with CV disease do not estimate diet quality more accuracy than those without CV disease. Among adults with CV disease, misperceptions in diet quality were associated with worse CV risk factor profiles, highlighting the need to assess and educate patients with CV disease on personal diet quality as part of healthy lifestyle promotion. Among those without CV disease, dietary misperceptions were associated with higher BMI, suggesting that increasing awareness of one's diet is also important in CV disease prevention.