Background The cause of heart failure with preserved ejection fraction (HFpEF) is poorly understood, and specific therapies are lacking. Previous studies suggested that inflammation plays a role in the development of HFpEF. Herein, we aimed to investigate in community-dwelling individuals whether a higher plasma interleukin 6 (IL-6) level is associated with an increased risk of developing new-onset heart failure (HF) over time, and specifically HFpEF. Methods and Results We performed a case-cohort study based on the PREVEND (Prevention of Renal and Vascular End-Stage Disease) study, a prospective general population-based cohort study. We included 961 participants, comprising 200 participants who developed HF and a random group of 761 controls. HF with reduced ejection fraction or HFpEF was defined on the basis of the left ventricular ejection fraction of ≤40% or >40%, respectively. In Cox proportional hazard regression analyses, IL-6 levels were statistically significantly associated with the development of HF (hazard ratio HR, 1.28; 95% CI, 1.02-1.61; =0.03) after adjustment for key risk factors. Specifically, IL-6 levels were significantly associated with the development of HFpEF (HR, 1.59; 95% CI, 1.16-2.19; =0.004), whereas the association with HF with reduced ejection fraction was nonsignificant (HR, 1.05; 95% CI, 0.75-1.47; =0.77). In sensitivity analyses, defining HFpEF as left ventricular ejection fraction ≥50%, IL-6 levels were also significantly associated with the development of HFpEF (HR, 1.47; 95% CI, 1.04-2.06; =0.03) after adjustment for key risk factors. Conclusions IL-6 is associated with new-onset HFpEF in community-dwelling individuals, independent of potential confounders. Our findings warrant further research to investigate whether IL-6 might be a novel treatment target to prevent HFpEF.