Atherosclerosis involves both innate and adaptive immunity. Here, we provide an overview of the role of regulatory T (Treg) cells in atherosclerotic diseases. Treg cells and their inhibitory cytokines, IL-10 and TGF-β, have been identified in atherosclerotic lesions and to inhibit progression through lipoprotein metabolism modulation. Treg cells have also been found to convert to T follicular helper (Tfh) cells and promote atherosclerosis progression. Treg cell involvement in different stages of atherosclerotic progression and Treg cell-mediated modulation of plaque development occurs via inflammation suppression and atheroma formation has been focused. Moreover, existing knowledge suggests that Treg cells are likely involved in the pathology of other specific circumstances including in-stent restenosis, neointimal hyperplasia, vessel graft failure, and ischemic arterial injury; however, there remain gaps regarding their specific contribution. Hence, advancements in the knowledge regarding Treg cells in diverse aspects of atherosclerosis offer translational significance for the management of atherosclerosis and associated diseases.