Mitral insufficiency (MI) is difficult to quantify, due to cardiac motion and complex regurgitation patterns. This study evaluated the use of 4D flow MRI with semi-automated retrospective valve tracking for assessment of severe MI. Valve tracking of both the mitral and aortic valve allowed for direct measurement of retrograde flow and indirect measurement based on total left-ventricular inflow and aortic outflow. Conventional 2D MRI-based indirect quantification was used as a reference. Eccentric regurgitation patterns complicated direct quantification, necessitating manual plane angulation for accurate measurement. Indirect quantification corresponded well with 2D MRI and might be a more reproducible alternative.