Dnmt2 is a highly conserved methyltransferase of uncertain biological function(s). As Dnmt2 was considered as a driver of fruit fly longevity and a modulator of stress response, we decided to evaluate the role of Dnmt2 during stress‐induced premature senescence in NIH3T3 mouse fibroblasts. Stable knockdown of Dnmt2 resulted in hydrogen peroxide‐mediated sensitivity and apoptosis, whereas in the control conditions, senescence was induced. Cellular senescence was accompanied by elevated levels of p53 and p21, decreased telomere length and telomerase activity, increased production of reactive oxygen species and protein carbonylation, and DNA damage. Dnmt2 silencing also promoted global DNA and RNA hypermethylation, and upregulation of methyltransferases, namely Dnmt1, Dnmt3a, and Dnmt3b. Taken together, we show for the first time that Dnmt2 may promote lifespan in the control conditions and survival during stress conditions in mouse fibroblasts. Dnmt2 silencing results in cellular senescence and apoptosis in the control conditions and after HP treatment, respectively. Senescence was accompanied by mild oxidative stress, DNA damage and telomere shortening, whereas Dnmt2‐silenced fibroblasts were more prone to ROS‐induced apoptotic cell death after HP stimulation.