Dysregulation of macrophage-mediated inflammatory responses is central to sepsis pathogenesis, making its modulation crucial for reducing organ damage and mortality. This study reveals that the key serine synthesis enzyme phosphoglycerate dehydrogenase (PHGDH), known for regulating tumor and immune cell functions, is significantly downregulated in mouse macrophages following lipopolysaccharide (LPS) stimulation, as well as in patients with systemic inflammatory response syndrome or sepsis. PHGDH knockdown enhances inflammatory responses to LPS and Escherichia coli in vitro, while myeloid PHGDH knockout exacerbates inflammation and organ damage in septic mouse models. In contrast, deficiency in serine and its derivative glycine inhibits LPS-induced macrophage inflammation both in vitro and in vivo. Mechanistically, PHGDH interacts with transforming growth factor-β-activated kinase 1 (TAK1), inhibiting TAK1 binding to TAK1-binding protein, thereby suppressing the TAK1-NF-κB/MAPK signaling pathway. Furthermore, adeno-associated virus-mediated PHGDH overexpression in lung macrophages reduces sepsis-related inflammation and damage, highlighting PHGDH's nonmetabolic role in regulating macrophage-mediated inflammation and suggesting new therapeutic strategies for sepsis treatment.Copyright © 2025 The Authors. Published by Elsevier Inc. All rights reserved.