Systems, devices and methods for repairing a native heart valve. In one embodiment, a repair device for repairing a native mitral valve having an anterior leaflet and a posterior leaflet between a left atrium and a left ventricle comprises a support having a contracted configuration and an extended configuration. In the contracted configuration, the support is sized to be inserted under the posterior leaflet between a wall of the left ventricle and chordae tendineae. In the extended configuration, the support is configured to project anteriorly with respect to a posterior wall of the left ventricle by a distance sufficient to position at least a portion of the posterior leaflet toward the anterior leaflet.