A 51-year-old man was referred to our cardiology department for examination of a systolic murmur. Physical examination indicated a grade 3 systolic murmur at the fourth left intercostal space. Transthoracic echocardiography (TTE; Figure 1A) and heart dynamic computed tomography (Figure 1B) demonstrated a double-orifice mitral valve (DOMV) with 4 papillary muscles (triangles). Two valve orifices were separated by a complete bridge (arrow). The posteromedial mitral valve was larger, and the anterolateral mitral valve was smaller. The anterior leaflet of the anterolateral mitral valve prolapsed owing to chordae rupture, while color Doppler showed severe mitral regurgitation (Figure 2, Movie I in the online-only Data Supplement). No other combined congenital\nabnormalities were detected. Three-dimensional TTE clearly showed two orifices of the mitral valve (Movie II in the online-only Data Supplement). Transesophageal echocardiography (TEE) confirmed the diagnosis of DOMV and mitral valve prolapse (Figure 3). Three-dimensional TEE provided a better understanding of the mitral valve and the prolapsed leaflet (Figure 4, Movie III in the online-only Data Supplement).