ABSTRACT Our objective was to investigate the effect of cholesterol [hypercholesterolemia and 7‐ketocholesterol (7K)] on endoglin (Eng) expression and regulation with respect to endothelial or vascular dysfunction in vivo and in vitro. In vivo experiments were performed in 2‐mo‐old atherosclerosis‐prone apolipoprotein E–deficient/LDL receptor–deficient (ApoE −/− /LDLR −/− ) female mice and their wild‐type C57BL/6J littermates. In in vitro experiments, human aortic endothelial cells (HAECs) were treated with 7K. ApoE −/− /LDLR −/− mice developed hypercholesterolemia accompanied by increased circulating levels of P‐selectin and Eng and a disruption of NO metabolism. Functional analysis of the aorta demonstrated impaired vascular reactivity, and Western blot analysis revealed down‐regulation of membrane Eng/Smad2/3/eNOS signaling in ApoE −/− /LDLR −/− mice. 7K increased Eng expression via Krüppel‐like factor 6 (KLF6), liver X nuclear receptor, and NF‐&x03BA;B in HAECs. 7K‐induced Eng expression was prevented by the treatment with 2‐hydroxypropyl‐β‐cyclodextrin; 8‐{[5‐chloro‐2‐(4‐methylpiperazin‐1‐ yl ) pyridine‐4‐carbonyl] amino}‐1‐(4‐fluorophenyl)‐4, 5‐dihydrobenzo[g]indazole‐3‐carboxamide; or by KLF6 silencing. 7K induced increased adhesion and transmigration of monocytic human leukemia promonocytic cell line cells and was prevented by Eng silencing. We concluded that hypercholesterolemia altered Eng expression and signaling, followed by endothelial or vascular dysfunction before formation of atherosclerotic lesions in ApoE −/− /LDLR −/− mice. By contrast, 7K increased Eng expression and induced inflammation in HAECs, which was followed by an increased adhesion and transmigration of monocytes via endothelium, which was prevented by Eng inhibition. Thus, we propose a relevant role for Eng in endothelial or vascular dysfunction or inflammation when exposed to cholesterol.—Vicen, M., Vitverova, B., Havelek, R., Blazickova, K., Machacek, M., Rathouska, J., Najmanová, I., Dolezelova, E., Prasnicka, A., Sternak, M., Bernabeu, C, Nachtigal, P. Regulation and role of endoglin in cholesterol‐induced endothelial and vascular dysfunction in vivo and in vitro . FASEB J. 33, 6099–6114 (2019). www.fasebj.org