Background. Significant numbers of asymptomatic hypertensive patients are attacked by subclinical target organ damage (TOD) such as proteinuria, left ventricular hypertrophy and carotid atherosclerosis. Platelets become activated in uncontrolled hypertension and play a crucial role in increased thrombotic tendency. Mean platelet volume (MPV) is one of the markers that correlate closely with platelet activity. We aimed to investigate the relationship between MPV levels and subclinical TOD in newly diagnosed hypertensive patients. Methods. 80 newly diagnosed hypertensive patients were enrolled to this cross-sectional study. Ambulatory blood pressure monitoring was performed for all patients. Left ventricular mass index (LVMI), carotid intima-media thickness (IMT) and urine albumin/creatinine ratio (UACR) were measured as indices of cardiac, vascular and renal damage, respectively. MPV was measured from blood samples collected in EDTA tubes and high-sensitivity C reactive protein (hs-CRP) was measured by using nephlometer. Results. MPV was significantly correlated with 24-h systolic-diastolic blood pressure (r = 0.52 and r = 0.55, respectively). Correlation analysis indicated that MPV was moderately related with UACR, LVMI, carotid IMT and hs-CRP (r = 0.50, r = 0.55, r = 0.60 and r = 0.69, respectively, p = 0.0001). Multivariable analysis identified that MPV levels were independently associated with severity of proteinuria, carotid IMT and LVMI (p = 0.001). Conclusion. Our findings suggested that MPV levels were associated with severity of subclinical TOD including; carotid atherosclerosis, left ventricular hypertrophy and renal damage, in hypertensive patients. In addition to this, MPV levels were significantly correlated with hs-CRP levels and 24-h ambulatory blood pressure measurements.