Abstract—Mitochondria are a major site of reactive oxygen species production, which may contribute to the development of cardiovascular disease. Protecting mitochondria from oxidative damage should be an effective therapeutic strategy; however, conventional antioxidants are ineffective, because they cannot penetrate the mitochondria. This study investigated the role of mitochondrial oxidative stress during development of hypertension in the stroke-prone spontaneously hypertensive rat, using the mitochondria-targeted antioxidant, MitoQ₁₀. Eight-week–old male stroke-prone spontaneously hypertensive rats were treated with MitoQ₁₀ (500 µmol/L; n=16), control compound decyltriphenylphosphonium (decylTPP; 500 µmol/L; n=8), or vehicle (n=9) in drinking water for 8 weeks. Systolic blood pressure was significantly reduced by 25 mm Hg over the 8-week MitoQ₁₀ treatment period compared with decylTPP (F=5.94; P=0.029) or untreated controls (F=65.6; P=0.0001). MitoQ₁₀ treatment significantly improved thoracic aorta NO bioavailability (1.16±0.03 g/g; P=0.002, area under the curve) compared with both untreated controls (0.68±0.02 g/g) and decylTPP-treated rats (0.60±0.06 g/g). Cardiac hypertrophy was significantly reduced by MitoQ₁₀ treatment compared with untreated control and decylTPP treatment (MitoQ₁₀: 4.01±0.05 mg/g; control: 4.42±0.11 mg/g; and decylTPP: 4.40±0.09 mg/g; ANOVA P=0.002). Total MitoQ₁₀ content was measured in liver, heart, carotid artery, and kidney harvested from MitoQ₁₀-treated rats by liquid chromatography-tandem mass spectrometry. All of the organs analyzed demonstrated detectable levels of MitoQ₁₀, with comparable accumulation in vascular and cardiac tissues. Administration of the mitochondria-targeted antioxidant MitoQ₁₀ protects against the development of hypertension, improves endothelial function, and reduces cardiac hypertrophy in young stroke-prone spontaneously hypertensive rats. MitoQ₁₀ provides a novel approach to attenuate mitochondrial-specific oxidative damage with the potential to become a new therapeutic intervention in human cardiovascular disease.