Although proteinuria is a well-known risk factor for cardiovascular disease, its relationship with the progression of aortic stenosis (AS) has not been established. Our aim was to investigate the relationship between proteinuria (detected by urine dipstick test) and AS progression (assessed by the annualized reduction rate of aortic valve area [AVA]). A total of 460 patients with mild to moderate AS (defined by a peak velocity of 2.0–4.0 m/s) without end-stage renal disease who underwent two echocardiograms at least 3 months apart were included. The progression of AS was significantly faster in patients with proteinuria than those without (108 patients vs. 352 patients; annualized reduction rate of AVA, − 7.7 ± 13.5% vs. − 4.5 ± 11.6%; p = 0.017). The relationship between the presence of proteinuria and the accelerated progression of AS was significant among patients with estimated glomerular filtration rate (eGFR) ≥ 60 mL/min/1.73 m² (− 11.0 ± 17.5% vs. − 4.2 ± 10.0%; p < 0.001), but not among those with eGFR 15–60 mL/min/1.73 m² (− 5.8 ± 10.3 vs. − 5.3 ± 14.8%; p = 0.822). When stratified by the presence of diabetes, the association of proteinuria with AS progression was only significant in patients without diabetes (− 8.1 ± 12.0% vs. − 8.1 ± 15.7%; p = 0.018). Multivariable logistic regression analysis identified that the presence of proteinuria was an independent predictor of AS progression. The progression of AS was accelerated in patients with mild to moderate AS and proteinuria, particularly among those with preserved renal function and no diabetes.