Background and Objectives: Moderate aortic stenosis (AS) confers a surprisingly adverse prognosis, approaching that of severe AS. The objective of this study was to describe the clinical course of patients with moderate AS with evidence of concomitant heart failure manifesting as elevated brain natriuretic peptide (BNP) levels. Methods: This is a single-center, retrospective cohort study of 332 patients with elevated BNP. 165 patients with moderate AS were compared with 167 controls with none-mild AS.The Median follow-up duration was 3.85 years. The primary outcome was a composite endpoint of all-cause hospitalizations and all-cause mortality. Results: BNP levels were 530 and 515 pg/mL in the study and the control groups, respectively. Moderate AS had significantly higher rates of primary composite endpoint in both univariate analysis (hazard ratio [HR], 1.50; 95% confidence interval [CI], 1.14–1.97; p=0.004) and adjusted analysis (HR, 1.45; 95% CI, 1.05–2.01; p=0.02). Moderate AS had 1.41 (95% CI, 1.18– 1.69; p<0.001) times more all-cause hospitalization per patient-year of follow-up compared to controls in the univariate model. After adjustment for significant covariates, moderate AS remained an independent predictor of all-cause hospitalizations (incidence rate ratio [IRR], 1.45; 95% CI, 1.18–1.79; p=0.005). Furthermore, moderate AS was significantly associated with higher all-cause hospitalization rates in both heart failure with reduced ejection fraction (IRR, 1.33; 95% CI, 1.02–1.75; p=0.038) and heart failure with preserved ejection fraction [IRR], 1.31; 95% CI, 1.03–1.67; p=0.026). Conclusions Moderate AS in conjunction with elevated BNP portends a significantly worse prognosis than those without moderate AS and should be followed closely.