Alterations in epigenomic patterns are associated with diverse physiological functions and pathological mechanisms causing aging-related diseases, such as degenerative disorders and cancers. We investigated the senescent effects of BIX01294, a G9a (histone methyltransferase) inhibitor, in human bone marrow mesenchymal stromal cells (hBM-MSCs). We determined the optimal dose and time of BIX01294 treatment in hBM-MSCs to be 1 μM and 12 h, respectively. Under these conditions, the expression of the antisenescent genes TERT, bFGF, VEGF, and Oct-4 increased, whereas the expression of the senescent factors p16, p21, and p53 decreased. The number of β-galactosidase-positive cells decreased significantly, and the rates of migration and cellular protection against oxidative damage increased in BIX01294-treated MSCs. These data indicate that an optimized dose of BIX01294 may improve the potency and senescence of stem cells, which may improve the efficacy of stem cell therapy.