ABSTRACT Limited evidence exists on the relationship between dietary niacin intake and Life's Essential 8 (LE8), a new metric for cardiovascular health. We analyzed data from 23,729 adults aged ≥ 20 years from the 2005–2018 National Health and Nutrition Examination Survey (NHANES). The LE8 score (range: 0–100) reflects health behaviors, health factors, and biomarkers. After adjusting for confounders, each 10‐unit increase in niacin intake was associated with 0.65‐point higher LE8 score ( β = 0.65, 95% CI = 0.43–0.87; p < 0.001). Compared to the lowest tertile, the highest tertile of niacin intake had a 1.83‐point higher LE8 score ( β = 1.83, 95% CI = 1.02–2.64; p < 0.001). Restricted cubic spline analysis indicated a linear dose–response relationship (P‐nonlinearity = 0.578). Stratified analyses confirmed significant effect modification, with niacin‐LE8 associations most pronounced in geriatric strata ( β = 1.91, 95% CI = 1.08–2.74; P‐interaction = 0.002), amplified among non‐Hispanic Black ( β = 1.27, 95% CI = 0.64–1.91) and White ( β = 1.20, 95% CI = 0.77–1.64) populations versus attenuated effects in Mexican Americans ( p = 0.003), enhanced across socioeconomic gradients (highest PIR tertile: β = 1.08, 95% CI = 0.56–1.60; p = 0.025), and exhibiting 86% magnitude elevation in cardiovascular comorbidity subgroups ( β = 1.69, 95% CI = 0.59–2.79; p = 0.023). While these cross‐sectional findings suggest a beneficial relationship between dietary niacin intake and cardiovascular health, causality cannot be confirmed and residual confounding may remain. These findings may have implications for dietary guidance aimed at cardiovascular health at the population level.