Salvianic acid A (SAA) is an active water-soluble constituent derived from Salvia miltiorrhiza Bge that is used extensively in the treatment of angiocardiopathy in China. However, few reports have investigated the therapeutic effect and the underlying mechanisms of SAA on atherosclerosis (AS). This study examines the protective mechanisms of SAA on AS in vivo and in vitro. SAA treatment (3 and 10 mg/kg/d) prevented the progression of atherosclerotic lesions and decreased 58.2% and 72.8% of the lipid deposition in the aorta of high fat-diet-induced AS rat. Notably, SAA treatment ameliorated serum lipid abnormalities by decreasing 20.4% and 33.8% of triglyceride, 26.1% and 32.7% of total cholesterol, 36.0% and 57.3% of low-density lipoprotein-cholesterol levels and increasing 183.4% and 337.5% of high-density lipoprotein-cholesterol level in the serum of AS rat (all P <  0.05). SAA treatment lowered pro-inflammatory mediators including interleukin-1β, interleukin-6, tumor necrosis factor-α, intercellular cell adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) (all P <  0.05) by inhibiting the toll-like receptor 4/nuclear factor kappa B pathway. In addition, SAA treatment significantly decreased oxidative stress by increasing antioxidant enzymes activity, upregulating nuclear factor erythroid 2-related factor 2/heme oxygenase-1 pathway and downregulated expression of p47^phox and p22^phox (all P <  0.05) in vivo. Furthermore, SAA (10⁻⁵ and 3 × 10⁻⁵ M) suppressed oxidized low-density lipoprotein-induced expression of lectin-like oxidized low-density lipoprotein receptor-1, the phosphorylation of nuclear factor kappa B (p65), ICAM-1 and VCAM-1 (all P <  0.05) and inhibited NADPH oxidase subunit 4-mediated reactive oxygen species generation in human umbilical vein endothelial cells. The experimental data verify the protective role of SAA in AS and the underlying mechanisms are strongly associated with the inhibition of oxidative stress, inflammation, and amelioration of endothelial dysfunction.