Vascular dysfunction has emerged as a significant risk factor for the development of cardio- and cerebrovascular diseases (CVDs), which are currently the leading cause of morbidity and mortality worldwide. T-lymphocytes (T-cells) have been shown to be important modulators of vascular function in primary aging and CVDs, likely by producing inflammatory cytokines and reactive oxygen species that influence vasoprotective molecules. This review summarizes the role of T-cells on vascular function in aging, hypertension, and atherosclerosis in animals and humans, and discusses potential T-cell targeted therapeutics to prevent, delay, or reverse vascular dysfunction.