Macrophages are a primary immune cell involved in inflammation, and their cell plasticity allows for transition from an inflammatory to a reparative phenotype and is critical for normal tissue repair following injury. Evidence suggests that epigenetic alterations play a critical role in establishing macrophage phenotype and function during normal and pathologic wound repair. Here, we find in human and murine wound macrophages that cyclooxygenase 2/prostaglandin E 2 (COX-2/PGE 2) is elevated in diabetes and regulates downstream macrophage-mediated inflammation and host defense. Using single-cell RNA sequencing of human wound tissue, we identify increased NF-κB–mediated inflammation in diabetic wounds and show increased COX-2/PGE 2 in diabetic macrophages. Further, we identify that COX-2/PGE 2 production in wound macrophages requires epigenetic regulation of 2 key enzymes in the cytosolic phospholipase A 2/COX-2/PGE 2 (cPLA 2/COX-2/PGE 2) pathway. We demonstrate that TGF-β–induced miRNA29b increases COX-2/PGE 2 production via inhibition of DNA methyltransferase 3b–mediated hypermethylation of the Cox-2 promoter. Further, we find mixed-lineage leukemia 1 (MLL1) upregulates cPLA 2 expression and drives COX-2/PGE 2. Inhibition of the COX-2/PGE 2 pathway genetically (Cox2 fl/fl Lyz2 Cre+) or with a macrophage-specific nanotherapy targeting COX-2 in tissue macrophages reverses the inflammatory macrophage phenotype and improves diabetic tissue repair. Our results indicate the epigenetically regulated PGE 2 pathway controls wound macrophage function, and cell-targeted manipulation of this pathway is feasible to improve diabetic wound repair.