Interleukin (IL)-37 is a newly discovered member of the cytokine IL-1 family. Recent evidence suggests that IL-37, an anti-inflammatory factor, may have a role in atherosclerosis. In this study we used apoE-deficient diabetic mice, an established animal model, to examine the effects of IL-37 on the progression of vascular calcification and atherosclerosis. Compared with the control groups, IL-37-treated (with injection of recombinant protein for 16 weeks) animals had significantly less calcification areas detected by both von Kossa and Alizarin Red staining, and much smaller plaque size of the atherosclerotic lesions and lower plaque vulnerability scores detected by hematoxylin-eosin staining in the aorta root. Our data also showed that IL-37 treatment caused elevated concentrations of osteoprotegerin (OPG) in serum. We detected that the group that received additional anti-OPG antibody reduced the effect of IL-37 treatment. The group that received both IL-37 and anti-OPG had significant larger percentage area of calcified lesion and atherosclerotic plaque size than the IL-37-treated group. Significant changes in disease-relevant cytokines (eg, ALP, BMP-2, TNF-alpha, IL-18, and IL-10) were also elicited. This is the first report that IL-37 could attenuate not only atherosclerosis, but also vascular calcification. This study may offer a therapeutic potential for the prevention and treatment of calcification and atherosclerotic disease.