The accessibility of echocardiography and its ability to provide non-invasive information in real time make ultrasound the essential technique for evaluating diastolic function of the left ventricle. However, the diagnosis of diastolic dysfunction remains uncertain because echocardiographic indices may lead to divergent conclusions. During diastole, the mitral valve forces the left intraventricular flow to create a vortex. In healthy subjects, this vortex naturally redirects blood flow to the left ventricular outflow tract and helps the transition from filling to ejection. When the filling is impaired (diastolic dysfunction), a change in blood flow occurs, with a significant impact on the intraventricular vortex. The aim of this study is to reconstruct the 3D intraventricular blood flow to assist in the diagnosis of diastolic dysfunction. Color Doppler mode provides partial information of the velocity field since only the velocity components projected along the ultrasonic beams are available. To reconstruct the 3D intraventricular flow, we propose to generalize the method previously developed in 2D by [Assi et al, Physics in Medicine and Biology, 2017] which enables the reconstruction of a 2D flow through an optimization method based on fluid mechanics equations (continuity equation, boundary conditions?). From echocardiographic B-mode and color Doppler images acquired in tri-plane mode, volumetric three-component velocities can be reconstructed. Our algorithm was validated on a simulated three-dimensional Hill?s vortex ring. The 3D vertical flows were adequately recovered. The normalized velocity errors were ranged between 8 and 20% for acquisition angles in [-15°, 15°]. The next step is to validate the proposed method on a realistic patient-specific model of the intraventricular blood flow developed by the team [Chnafa et al, Computers & Fluids, 2014].