To date, the association between Life's Crucial 9 (LC9) and incidence of atrial fibrillation (AF) has not been explored. This study aimed to investigate the association between LC9 and the incidence of AF and evaluate the potential role of genetic risk.LC9 consists of 9 elements categorized as low, medium, and high cardiovascular health (CVH). Polygenic risk scores (PRSs) were categorized as low, medium, or high. A Cox proportional hazards regression model was used to determine the association between LC9 and incidence of AF. The combined effects and interactions between LC9 and AF PRS on incidence of AF were also examined.During the median follow-up of 12.87 years, 11,141 patients developed AF. Moderate CVH (hazard ratio [HR], 0.75; 95% confidence interval [CI], 0.70, 0.79) and high CVH (HR, 0.66; 95% CI, 0.62, 0.71) were associated with a reduced risk of AF, respectively, compared with those with low CVH. Individuals with a high CVH and low PRS exhibited the lowest risk of AF compared with those with low CVH and high PRS (HR, 0.55; 95% CI, 0.47, 0.64). Additive interactions between low-to-moderate CVH and high PRS were found (relative excess risk caused by interaction: 95% CI, 1.45 [0.75, 2.15] and 0.60 [0.28, 0.92]; attributable proportion caused by interaction: 95% CI, 0.25 [0.15, 0.35] and 0.14 [0.06, 0.21], respectively).Higher LC9 scores were associated with a decreased risk of AF. Adherence to the LC9 guidelines may help reduce the incidence of AF, regardless of genetic risk.