The effects of aldosterone receptor blockade on echocardiography in spontaneously hypertensive rats (SHR) are not fully characterized. In this study, multiple echocardiographic parameters were compared for 42 weeks between SHR versus Wistar-Kyoto rats (WKY) serving as normotensive controls. In addition, echocardiographic parameters were compared for 28 weeks between the SHR versus SHR treated with eplerenone 100 mg/kg/day or spironolactone 50 mg/kg/day. Compared to normotensive WKY rats, SHRs had significantly increased systolic blood pressure, increased cardiac mass, increased isovolumic relaxation time (IVRT), decreased E/A ratio, increased mitral closure opening time interval (MCO) and increased Tei index. Both eplerenone and spironolactone significantly decreased systolic blood pressure compared to the SHR controls. The spironolactone treatment group demonstrated significant increases in heart rate and cardiac output and a decrease in cardiac index compared to SHR controls. Any aldosterone blockade in SHR protected against the increased cardiac mass. Similar to clinical echocardiographic observations, hypertension in rats results in left ventricular hypertrophy (LVH) and diastolic dysfunction and aldosterone receptor blockade reduces LVH in SHR.