Objective— Tissue inhibitor of metalloproteinase 3 (TIMP3) is a stromal protein that inhibits the activity of proteases and receptors. TIMP3 is downregulated in metabolic and inflammatory disorders, such as type 2 diabetes mellitus and atherosclerosis, particularly in regions enriched with monocyte/macrophage cells. To investigate the role of TIMP3 in atherosclerosis, we generated a new mouse model in which Timp3 was overexpressed in the atherosclerotic plaque via a macrophage-specific promoter (MacT3). We elucidated any potential antiatherosclerotic effects of TIMP3, including regulation of monocyte/macrophage recruitment within atherosclerotic plaques, in MacT3 mice crossbred with low-density lipoprotein receptor knockout (LDLR ^−/− ) mice. Methods and Results— MacT3/LDLR ^−/− mice had an improvement of atherosclerosis and metabolic parameters compared with LDLR ^−/− . En face aorta and aortic root examination of MacT3/LDLR ^−/− mice revealed smaller atherosclerotic plaques with features of stability, such as increased collagen content and decreased necrotic core formation. Atherosclerotic plaques in MacT3/LDLR ^−/− mice contained fewer T cells and macrophages. Furthermore, TIMP3 overexpression in macrophages resulted in reduced oxidative stress signals, as evidenced by lower lipid peroxidation, protein carbonylation, and nitration in atheromas. Conclusion— Our study confirmed that macrophage-specific overexpression of TIMP3 decreases the inflammatory content and the amplitude of atherosclerotic plaques in mice.