Background In our ageing society, valvular heart diseases (VHD) have become an increasing public health problem. However, the lack of studies describing the impact of these diseases on the outcome of very old subjects makes it difficult to appreciate their real clinical burden. Methods Prospective, observational, population-based cohort study in Belgium. Five hundred fifty six subjects aged 80 years and older were followed up for 5.1 ± 0.25 years for mortality and 3.0 ± 0.25 years for hospitalization. Echocardiograms were performed at baseline. The Cumulative Illness Rating Scale (CIRS) was calculated for each subject. Results The prevalence of moderate-to-severe VHD was 17 % (n = 97). Mitral stenosis was more prevalent in women and an age-dependent increase of the prevalence of severe aortic stenosis was seen. The overall disease burden was higher in participants with VHD (median CIRS 3 [IQR 3–5] vs 4 [IQR 3–6] (P = 0.008)). Moderate-to-severe VHD, and more specifically mitral stenosis and aortic stenosis, was found to be an independent predictor of both all-cause (HR 1.42 (95 % CI 1.04–1.95)) and cardiovascular mortality (HR 2.13 (95 % CI 1.38–3.29)). Moderate-to-severe VHD was also found to be an independent predictor of the need for a first unplanned hospitalization (HR 1.43 (95 % CI 1.06–1.94)). Conclusions A high prevalence of moderate-to-severe VHD was found in the very old. Moderate-to-severe VHD was identified as an independent risk factor for all-cause and cardiovascular mortality and as well for unplanned hospitalizations, independent of other structural cardiac abnormalities, ventricular function and major co-morbidities.