The mitral valve surgery decision is made mainly according to echocardiographic (ECHO) criteria. As the asymptomatic patients are still candidates for surgery in some situations, this makes the accurate assessment of mitral regurgitation (MR) severity and cardiac dimensions even more important. We aimed to compare ECHO and cardiac magnetic resonance imaging (CMR) in the assessment of MR severity and cardiac dimensions. In this prospective study, we included all patients with more than mild MR by ECHO and referred to our university hospital from 1st of April 2017 and 1st of April 2019. Exclusion criteria were critically ill patients, presence of other valve lesions, planned revascularization, pregnancy and contraindication for CMR. All patients had full history taking, examination, body surface area, and ECG. MR severity and left atrial and left ventricular dimensions were assessed in 50 patients with both 2D-ECHO and CMR in the same day. There were no significant differences in baseline clinical characteristics between moderate (24 patients) and severe MR (26 patients) groups. Poor degree of agreement was present between CMR and ECHO assessment for MR severity (same degree of MR only in 36% (18/50 patients) with kappa grade = 0.19). Furthermore, ECHO overestimated grades of MR compared to CMR (severe MR in 52% vs. 38.4%, p = 0.01 respectively). Based on the etiology of MR, primary (30 patients) vs. secondary MR (20 patients) showed the same dis-agreement between CMR and ECHO assessment of MR severity. Left atrial and ventricular dimensions showed good agreement between CMR and ECHO. Our results suggest that CMR could be more accurate than ECHO in assessing the severity of MR especially in severe cases that need surgery.