【】Purpose? This study aimed to employ transthoracic three-dimensional echocardiography for the quantitative evaluation of mitral valve configuration in patients with atrial and ventricular functional mitral regurgitation . Methods? A cohort of 68 VFMR patients and 53 AFMR patients, diagnosed at the Department of Cardiovascular Medicine, the First Clinical Medical College of Three Gorges University, constituted the VFMR and AFMR groups. Additionally, 50 age-matched healthy volunteers were included as the control group. Mitral valve parameters, including anterior-posterior diameter (AP), anterior leaflet-to-posterior leaflet diameter (ALPM), annular height (AH), annular circumference (CD), annular area (AA), non-planar angle (NPA), anterior leaflet area (ALA), posterior leaflet area (PLA), total leaflet area (TLA), tenting volume (VTent), tenting height (HTent), and posterior leaflet angle (PLθ), were quantitatively assessed using transthoracic real-time three-dimensional echocardiography. Statistical analysis was performed to assess the significance of differences in these parameters among the groups. Results In comparison to the control group, both AFMR and VFMR groups exhibited significantly increased values in AP, ALPM, AP/ALPM, AH, CD, AA, NPA, ALA, PLA, TLA, and PLθ, with a decreased TLA/AA ratio observed in the AFMR group. The VFMR group demonstrated smaller VTent and HTent, while the AFMR group showed larger VTent and HTent, all demonstrating statistical significance (P < 0.05). VFMR group values for AP, ALPM, AP/ALPM, ALA, PLA, TLA, VTent, HTent, and TLA/AA were greater than those of the AFMR group, while PLθ was smaller in the VFMR group, all with statistical significance (P < 0.05). Conclusion Mitral annular dilation, flattening, and compensatory leaflet enlargement were identified as common alterations in functional mitral regurgitation. In comparison to AFMR, VFMR presented with a more circular mitral annular shape, more pronounced leaflet and chordal tenting enlargement, with less prominent posterior leaflet tethering. The application of transthoracic real-time three-dimensional echocardiography enables non-invasive and quantitative assessment of mitral valve configuration in patients with atrial and ventricular functional mitral regurgitation, providing valuable insights for clinical decision-making.