BACKGROUND: Cardiac damage (CD) is prevalent across the spectrum of aortic stenosis (AS) and is a strong predictor of adverse outcomes. The natural history of CD in early AS and drivers of its progression, are poorly defined. We aimed to identify predictors and the prognostic significance of CD progression in patients with non-severe AS. METHODS: This was a single centre cohort study with longitudinal follow-up. Patients with mild or moderate AS at baseline and over serial echocardiographic follow-up were evaluated for the presence and progression of CD over time. RESULTS: 1751 patients were included. At baseline, CD was present in 1320 (75%), categorized as stage 1 in 231 (13%), stage 2 in 672 (38%), stage 3 in 109 (6%) and stage 4 in 308 (18%). Over a median follow-up of 2.1 [Q1-Q3 1.1-3.6] years, the prevalence of advanced-stage (stages 3 and 4) CD increased from 24% to 30%. Factors associated with progression to advanced-stage CD included comorbidity burden (adjusted OR [aOR] 1.23 per additional comorbidity; 95% CI: 1.10-1.38; p < 0.001) and the presence of atrial fibrillation (aOR 3.23; 95% CI: 1.15-9.07, p = 0.024) or left atrial dilation (aOR 1.55; 95% CI: 1.11-2.16, p = 0.010)], but not AS severity. Progression of CD was independently associated with all-cause mortality (adjusted HR [aHR] 1.35; 95% CI: 1.07-170; p = 0.012). CONCLUSIONS: In non-severe AS, CD is common and frequently progresses over time. CD progression appears to be driven by comorbidities and pre-existing myocardial remodelling and is an independent predictor of all-cause mortality.