Catheter-based percutaneous edge-to-edge repair using the MitraClip device (Abbott Vascular; Abbott Park, IL, USA) is a well-established, effective, and safe procedure that can be utilized in selected patients with mitral regurgitation (MR). The procedure mimics Alfieri’s surgical technique, bringing the anterior and posterior leaflets together from beneath the valve with a metallic stitch. Echocardiographic evaluation before the procedure is of paramount importance in defining the complex morphology of the valve and in detecting target leaflet lesion. Intra-procedural monitoring (i.e. delivery and placement of the clip) is usually performed under fluoroscopic and two-dimensional transoesophageal echocardiography. With the introduction of real-time three-dimensional transesophageal echocardiography (3D TEE), it appeared evident that the new technique would provide unique additional anatomical information both in selecting patients and guiding the procedure. In the selection of patients, the complex spatial structure of the valve is displayed as it actually is, allowing a precise assessment of the culprit as well as of secondary lesions. During the procedure, it has the unique ability to depict the “whole” scenario in which the procedure takes place in a single three-dimensional, real-time, easily understandable perspective. In this chapter we describe the normal mitral valve anatomy as displayed by 3D TEE, the 3D TEE pre-procedural characterization of valve morphology and the growing role of RT TEE in any individual steps of this complex procedure.