The invention relates to a prosthetic heart valve (100) for an endoprosthesis (1) used in the treatment of a stenotic cardiac valve and/or a cardiac valve insufficiency. The prosthetic heart valve (100) comprises of a plurality of leaflets (102), which consist of a natural and/or synthetic material and have a first opened position for opening the heart chamber and a second closed position for closing the heart chamber, the leaflets (102) being able to switch between their first and second position in response to the blood flow through the heart. In addition, the prosthetic heart valve (100) comprises a leaflet support portion (103), consisting of biological and/or synthetic material for mounting of the prosthetic heart valve (100) to a stent (10), and a bendable transition area (104) which forms a junction between the leaflets (102) and the leaflet support portion (103), the transition area (104) progressing essentially in a U-shaped manner similar to a cusp shape of a natural aortic or pulmonary heart valve for reducing tissue stresses during opening and closing motion of the leaflets (102). The invention further relates to an endoprosthesis (1) comprising a prosthetic heart valve (100) and a stent (10).