Cardiovascular disease (CVD) is a major cause of morbidity and mortality around the world. The risk factors and treatments have been thoroughly researched and documented, but one crucial element is endothelial dysfunction. Endothelial dysfunction is defined by the reduction of NO-induced vasodilation. The strongest link between endothelial dysfunction and CVD is atherosclerosis. The relationship between endothelial dysfunction and CVD has been solidified by reviewing the mechanisms that cause endothelial dysfunction as well as the major therapies that have shown that reducing or protecting against endothelial dysfunction can lead to better clinical outcomes in relation to CVD.