BACKGROUND: Moderate or worse paravalvular regurgitation (PVR) post transcatheter aortic valve replacement (TAVR) is associated with increased mortality. The mechanisms by which this occurs are not fully understood. AIMS: The aim of this study was to determine the mechanism by which PVR leads to worse outcomes. METHODS: A total of 1,974 intermediate-risk patients who received TAVR in the PARTNER 2 trial and registries were grouped by PVR severity. Clinical and echocardiographic outcomes were compared. RESULTS: Overall 1,176 (60%) patients had none/trace, 680 (34%) had mild, and 118 (6%) had ≥moderate PVR. At two years, ≥moderate PVR patients had increased risks of all-cause (HR 2.33 [1.41-3.85], p-value=0.001) and cardiovascular death (HR 3.30 [1.74-6.28], p-value <0.001), rehospitalisation (HR 2.68 [1.57-4.58], p-value <0.001), and reintervention (HR 14.72 [3.13-69.32], p-value <0.001). Moderate or worse PVR was associated with larger increases in left ventricular (LV) end-diastolic and systolic dimensions and volumes, LV mass indices, and reductions in LV ejection fractions (LVEFs) from 30 days to two years. Mild PVR was not associated with worse outcomes. Adjusting for LV dimensions and LVEF from the one-year echocardiogram, patients with ≥moderate PVR still had an increased risk of all-cause death or rehospitalisation at two years (HR 2.84 [1.25-5.78], p-value=0.009). CONCLUSIONS: Moderate or worse PVR, but not mild PVR, is associated with an increased risk of all-cause and cardiovascular death, rehospitalisation, and reintervention at two years. Moderate or worse PVR is also associated with adverse LV remodelling, which partially mediates how ≥moderate PVR leads to worse outcomes. These results provide dual insights on the deleterious impact of ≥moderate PVR and the contributing mechanisms of poor clinical outcomes.