The incidence of thromboembolism is higher in mitral regurgitation. Mean platelet volume (MPV), which is calculated automatically in the complete blood count tests, indicates platelet production, function and activation. Elevated MPV levels in cardiovascular diseases and some heart valve diseases have been shown before. We aimed to investigate the relationship between MPV and mitral regurgitation, and to evaluate the MPV levels according to the presence of atrial fibrillation or left atrial appendage thrombus in patients with mitral regurgitation for the first time. The study included 57 patients who had undergone transthoracic and transesophageal echocardiography for the classic symptoms and diagnosed with primary (organic) mitral regurgitation. The control group was composed of 46 age, sex and BMI-matched healthy individuals who had undergone transthoracic echocardiography and obtained normal findings. Echocardiographic evaluation was performed according to the recommendations of the American Echocardiography Society. Mean MPV values in patients with mitral regurgitation were significantly higher than the control group (P < 0.001). MPV levels and the thrombus risk were correlated with the severity of the disease. When the patients with mitral regurgitation were classified according to the presence of atrial fibrillation and left atrial appendage thrombus, patients with atrial fibrillation had higher MPV levels compared to patients with normal sinus rhythm (P < 0.001). In addition, highest MPV levels were found in patients with both atrial fibrillation and thrombosis (P < 0.001). In conclusion, measurement of MPV may be considered as a quick and reliable guide in the assessment of mitral regurgitation and thrombus, without any cost or any advanced expensive technology.