Background: Mitral regurgitation (MR) is the most commonly encountered valve lesion in modern clinical practice. Severe mitral regurgitation may cause systolic dysfunction. Left ventricular ejection fraction may not be an accurate measurement of LV function in patients with mitral insufficiency. Myocardial performance index (MPI) is a simple non invasive measure of myocardial function. Methods: The study involved 50 patients with valvular mitral regurgitation and 50 healthy subjects as a control group. Transthoracic echocardiography was carried out for all patients and control group. The echocardiographic measurements included left ventricular end diastolic and end systolic dimensions, left atrial diameter, ejection fraction (EF), and myocardial performance index (MPI). Results: Results revealed insignificant change in MPI between patients with mild MR and controls (26.47%), and significant changes in MPI between patients with moderate and severe mitral regurgitation and control group (29.41%, 41.17% respectively) with p value b0.05. Insignificant change in EF between patients with mild MR and controls (5.52%) was noted (p value N0.05), while the changes in EF between patients with moderate and severe mitral regurgitation and control groups were (−9.3%), (−7.4%) respectively with p value b0.05. Conclusion: Myocardial performance index is a good and easily determined index in the assessment of left ventricular function in patients with mitral regurgitation and has the ability to detect LV dysfunction earlier than ejection fraction.