Background: Aberrant endothelial function is a major contributing factor in cardiovascular disease. Dyslipidemia leads to decreased nitric oxide (NO) bioavailability, an early sign of endothelial failure. Lowinsulin gene enhancer protein (ISL1) levels decrease healthy NO bioavailability.We hypothesized that the microRNA miR-652-3p negatively regulates endothelial ISL1 expression and that dyslipidemia-induced miR-652-3p upregulation induces aberrant endothelial functioning via ISL1 downregulation. Methods: Various in vitro experiments were conducted in human umbilical vein endothelial cells (HUVECs). Luciferase assays were performed in HEK293 cells. We constructed a high-fat diet (HFD) Apoe−/− murine model of dyslipidemia and a rat model of low-density lipoprotein (LDL)-induced dyslipidemia to conduct in vivo and ex vivo experiments. Results: Luciferase assays confirmed miR-652-3p's targeting of the ISL1 3′-untranslated region (3′-UTR). Simvastatin blocked oxidized LDL (ox-LDL)-induced increases in miR-652-3p and ox-LDL-induced decreases in ISL1 protein expression, endothelial NO synthase (eNOS) activation, and NO production. Simvastatin's effects were abrogated by miR-652-3p overexpression and phenocopied by miR-652-3p inhibition. The dyslipidemic mouse model exhibited increased miR-652-3p and decreased ISL1 protein levels in the endothelium, effects opposed by simvastatin or miR-652-3p inhibition. The impact of simvastatin in vivo was abolished by overexpressing miR-652-3p or knocking-down ISL1. The rat model of dyslipidemia exhibited a similar pattern of miR-652-3p upregulation, attenuated ISL1 protein levels, decreased eNOS activation, and decreased NO production, effects mitigated by simvastatin. Conclusions:Dyslipidemia upregulates endothelialmiR-652-3p,which decreases ISL1 protein levels, eNOS activation, and NO production. Simvastatin therapy lowers endothelial miR-652-3p expression to protect endothelial function under dyslipidemic conditions.