Atherosclerosis is an inflammatory process due to oxidized low-density lipoprotein (oxLDL) accumulation in macrophages. We investigated the involvement of microRNAs in oxLDL accumulation and inflammatory response in macrophages. The expression of miR-146a decreases under oxLDL stimulation. MiR-146a significantly reduces intracellular LDL cholesterol content and secretion of interleukin 6, interleukin 8, chemokine (C-C motif) ligand 2 and matrix metallopeptidase 9. Toll-like receptor 4 (TLR4) is a relevant target of miR-146a, and miR-146a inhibits the activation of TLR4-dependent intracellular signaling pathways involved in cytoskeleton rearrangement, lipid uptake, and inflammatory cytokine secretion. These results indicate that miR-146a contributes to the regulation of both oxLDL accumulation and inflammatory response by negatively regulating TLR4 and thereby inhibiting the activation of TLR4-dependent signaling pathways. Over-expression of miR-146a may be useful in the prevention and treatment of atherosclerosis.