Phase separation, a biophysical segregation of subcellular milieus referred as condensates, is known to regulate transcription but its impacts on physiological processes are less clear. Here, we asked how the candidate phase regulator SGF29, a component of the transcriptional coactivator complex SAGA, regulates transcriptional events in aging. We 36 demonstrate that SGF29 forms liquid-like nuclear condensates as human mesenchymal 37 progenitor cells (hMPCs) become senescent. Mechanistically, SGF29 partitions with the 38 transcription factor SP1, RNA polymerase II and the transcriptional coactivator MED4 to form transcriptionally active condensates. These then target specific genomic loci, such as the CDKN1A promoter, to drive senescence-related gene expression. The Arg 207 in the intrinsically disordered region is identified as the key amino acid residue for SGF29 to form phase separation and activate CDKN1A transcription. Our study links phase separation to aging regulation and reveals nuclear condensates as a functional unit shaping transcriptional landscapes in aging.