Dyslipidemias are lipid metabolism alterations that cause increased levels of serum lipoprotein, cholesterol, and triglycerides. These alterations are associated with a higher incidence of cardiovascular diseases and are a risk factor for atherosclerosis development. This study aimed to evaluate the effect of Rosmarinus officinalis essential oil (EORO, 100 mg/kg) and its nanoemulsion (NEORO, 500 µg/kg) on Triton and coconut saturated-fat-induced (CSF) dyslipidemias using Wistar rats. The phytochemical evaluation of EORO performed by gas chromatography-mass spectroscopy (GC-MS) revealed 1,8-cineole (33.70%), camphor (27.68%), limonene (21.99%), and α-pinene (8.13%) as its major compounds. Triton-induced dyslipidemia significantly increased total cholesterol, LDL, and triglycerides levels. On the other hand, the groups treated with EORO and NEORO had significantly reduced total cholesterol, LDL, and triglycerides compared to the group treated only with Triton. Similar results were observed on the positive control treated with simvastatin. Dyslipidemia induced with coconut saturated-fat (CSF) caused abdominal fat gain, hypercholesterolemia, hypertriglyceridemia, increased LDL levels, and atherogenesis in the aorta. In contrast, the groups treated with EORO, NEORO, and simvastatin had significantly reduced hypercholesterolemia and hypertriglyceridemia, reduced abdominal fat gain, and absence of atherogenesis in the vascular endothelium. Overall, in the Triton-induced dyslipidemia model, EORO treatment had superior values than NEORO's (and simvastatin), although the differences were not too high, while in the CSF model, the values were mixed. In this manner, our results show an anti-dyslipidemic and anti-atherogenic activity effect by EORO and NEORO.