Mitral valve regurgitation (MVR) is common in patients receiving left ventricular assist device (LVAD) support, however the haemodynamic effect of MVR is not entirely clear. This study evaluated the haemodynamic effect of MVR with LVAD support and the influence of inflow cannulation site and LVAD speed modulation. Left atrial (LAC) and ventricular (LVC) cannulation was evaluated in a mock circulation loop with no, mild, moderate and severe MVR with constant speed and speed modulation (±600 RPM) modes. The use of an LVAD relieved pulmonary congestion during severe MVR, by reducing left atrial pressure from 20.5 to 10.8 (LAC) and 11.5 (LVC) mmHg. However, LAC resulted in decreased left ventricular stroke work (−0.08 J), ejection fraction (−7.9%) and higher MVR volume (+12.7 mL) and pump speed (+100 RPM) compared to LVC. This suggests that LVC, in addition to reducing MVR severity, also improves ventricular washout over LAC. LVAD speed modulation in synchrony with ventricular systole reduced MVR volume and increased ejection fraction with LAC and LVC, thus demonstrating the potential benefits of this mode, despite a reduction in cardiac output.