Updated project metadata. Upon antigen-specific T Cell Receptor (TCR) engagement, human CD4+ T cells proliferate and differentiate, a process associated with rapid transcriptional changes and metabolic reprogramming utilizing aerobic glycolysis together with maintenance of oxidative phosphorylation1,2. However, the role of glycolytic-reprogramming during T-cell activation remains largely unclear3,4,5. Here, we show that maintenance of cytosolic pyruvate production is an essential requirement for remodeling of the CD4+ T cell epigenome after TCR-engagement. Furthermore, we provide evidence that the local inflammatory environment sustains metabolic reprogramming of CD4+ T-cells and impacts histone modification in a pyruvate-dependent manner. Mechanistically, we demonstrate that rapid and sustained generation of cytosolic, but not mitochondrial, pyruvate is an essential step for acetyl-coA production and subsequent H3K27ac epigenome remodeling. TCR-activation was found to induce nuclear import of pyruvate dehydrogenase (PDH) and its association with both the p300 acetyltransferase and histone H3K27ac. Disrupting PDH nuclear import impacted expression of activation-induced genes. These results reveal a direct connection between CD4+ T cell metabolic reprogramming and transcriptional regulation, with the generation of cytosolic pyruvate being an essential step in T cell activation. These data support tight integration of metabolic enzymes and histone modifying enzymes, allowing metabolic reprogramming to fuel CD4+ T cell activation.