[Background] Extracellular vesicles (EV), a spherical particle released by cells and enclosed by a lipid-bilayer, contain various molecules and mediate cell-to-cell communication under both physiological and pathological conditions. In the present study, we aimed to clarify the changes in concentration, size, and molecular properties of plasma EV from spontaneously hypertensive rats (SHR). [Methods] Male Wistar Kyoto rats (WKY) and SHR at 5-7-week-old were used for collecting heparin-anticoagulated plasma and organs. Large EV (diameter: 150-1000 nm) were isolated from plasma by centrifugation (10000 x g). Small EV (diameter: 50-150 nm) were isolated by ultracentrifugation (164071 x g) after precipitation with polyethylene-glycol. The concentration and size distribution of EV were measured by a tunable resistive pulse sensing analysis. The expression level of EV marker proteins was measured by Western blotting. [Results] There was no significant difference in the concentration and size distribution of plasma EV between WKY and SHR. The expression of CD81 protein in plasma small EV from SHR was significantly lower than that from WKY. In left ventricle and skeletal muscle of SHR, the expression of CD81 protein was significantly lower than those of WKY. [Conclusion] Lower expression of CD81 in the left ventricle and skeletal muscle may indicate the plasma small EV origins which may partly explain the pathological mechanisms of high blood pressure in SHR.