Epigenetic regulation is essential for the maintenance of the hematopoietic system, and its deregulation is implicated in hematopoietic disorders. Here, we show that UTX, a demethylase for lysine 27 on histone H3 (H3K27) and a component of Compass-like and SWI/SNF complexes, plays an essential role in the hematopoietic system by globally regulating aging-associated genes. Utx-deficient (UtxΔ/Δ) mice exhibited myeloid skewing with dysplasia, extramedullary hematopoiesis, impaired hematopoietic reconstituting ability, and increased susceptibility to leukemia, which are the hallmarks of hematopoietic aging. RNA-sequencing (RNA-seq) analysis revealed that Utx deficiency converted the gene expression profiles of young hematopoietic stem-progenitor cells (HSPCs) to those of aged HSPCs. Utx expression in HSCs declines with age and UtxΔ/Δ HSPCs exhibited increased expression of an aging-associated marker, accumulation of reactive oxygen species, and impaired repair of DNA double-strand breaks. Pathway and chromatin immunoprecipitation (ChIP) analyses coupled with RNA-seq data indicated that UTX contributes to hematopoietic homeostasis mainly by maintaining the expression of genes downregulated with aging, via both demethylase-dependent and -independent epigenetic programming. Of note, comparison of pathway changes in UtxΔ/Δ HSPCs, aged muscle stem cells, aged fibroblasts, and aged iPS-induced neuronal cells showed substantial overlap, strongly suggesting common aging mechanisms among different tissue stem cells.