Fibroblast growth factor 21 (FGF-21) is an endocrine factor that can be secreted into circulation by the liver. FGF-21 takes part in metabolic actions and is thought to be a promising candidate for the treatment of diabetes. However, the role of FGF-21 in atherosclerosis is unknown. In this study, apoE^−/− mice were fed an atherogenic diet for 4 weeks with and without subcutaneous injections of FGF-21. ApoE^−/− mice fed an atherogenic diet showed hyperlipidemia, a large plaque area in aortas and increased vessel wall thickness. Plasma FGF-21 content and protein level of FGF receptor 1 (FGFR1) in aortas was greater in apoE^−/− than C57BL/6J mice. Exogenous FGF-21 treatment significantly ameliorated dyslipidemia in apoE^−/− mice. FGF-21–treated apoE^−/− mice showed reduced number of aortic plaques and plaque area as well as reduced number of TUNEL-positive cells. Protein levels of the endoplasmic reticulum stress markers glucose-regulated protein 94, caspase-12 and C/EBP homologous protein were reduced by 34.5, 31.4 and 26.5 %, respectively, in apoE^−/− mice. Endogenous expression of FGF-21 and its receptor FGFR1 were upregulated in apoE^−/− mice, and exogenous administration of FGF-21 ameliorated the atherogenic-induced dyslipidemia and vascular atherosclerotic lesions. FGF-21 protecting against atherosclerosis might be in part by its inhibitory effects on endoplasmic reticulum stress-mediated apoptosis.