The present disclosure is directed to embodiments of catheter-based prosthetic heart valves, and in particular, prosthetic heart valves having sealing devices configured to seal the interface between the prosthetic valve and the surrounding tissue of the native annulus in which the prosthetic valve is implanted. In one embodiment, a prosthetic heart valve includes an annular sealing member that can be placed in a delivery orientation extending axially away from one end of the valve when the valve is in a radially compressed state. When the valve is expanded, the expansion of the frame causes the sealing member to be pulled to an operative orientation covering a portion of the frame. The present disclosure also discloses new mechanisms and techniques for mounting valve leaflets to a frame of a prosthetic heart valve.