Epigenetic modifications are thought to be important for gene expression changes during development and aging. However, besides the Sir2 histone deacetylase in somatic tissues and H3K4 trimethylation in germlines, there is scant evidence implicating epigenetic regulations in aging. The insulin/IGF-1 signaling (IIS) pathway is a major life span regulatory pathway. Here, we show that progressive increases in gene expression and loss of H3K27me3 on IIS components are due, at least in part, to increased activity of the H3K27 demethylase UTX-1 during aging. RNAi of the utx-1 gene extended the mean life span of C. elegans by ∼30%, dependent on DAF-16 activity and not additive in daf-2 mutants. The loss of utx-1 increased H3K27me3 on the Igf1r/ daf-2 gene and decreased IIS activity, leading to a more “naive” epigenetic state. Like stem cell reprogramming, our results suggest that reestablishment of epigenetic marks lost during aging might help “reset” the developmental age of animal cells. ► Elevated utx-1 expression during aging preceded increases in daf-2 expression ► Reducing utx-1 gene expression extended the mean life span of C. elegans by ∼30% ► Life span extension induced by utx-1 RNAi depended on IIS pathway ► Reducing utx-1 level promoted H3K27me3 on daf-2 and a younger epigenetic state