The IGF-1R is a genetic determinant of oxidative stress and longevity. Hyperglycemia induces an exponential increase in the production of a key danger signal, reactive oxygen intermediates, which target genomic DNA. Here, we report for the first time that ligand activation of the IGF-1R prevents hyperglycemia induced genotoxic stress and enhances DNA repair, maintaining genomic integrity and cell viability. We performed single gel electrophoresis (comet assay) to evaluate DNA damage in serum starved SV40 murine mesangial cells (MMC) and normal human mesangial cells (NHMC), maintained at high ambient glucose concentration. Hyperglycemia inflicted an impressive array of DNA damage in the form of single-stranded breaks (SSBs) and double-stranded breaks (DSBs). The inclusion of IGF-1 to culture media of MMC and NHMC prevented hyperglycemia induced DNA damage. To determine if DNA damage was mediated by reactive oxygen species (ROS), ROS generation was evaluated, in the presence of IGF-1, or the free radical scavenger n-acetyl-cysteine (NAC). IGF-1 and NAC inhibited hyperglycemic induced ROS production and hyperglycemia induced DNA damage. We next asked whether IGF-1 promotes the repair of DSB under hyperglycemic conditions, by homologous recombination (HRR) or non-homologous end joining (NHEJ). Repair of DSB by NHEJ and HRR was operative in MMC maintained under hyperglycemic conditions. IGF-1 increased HRR by nearly 2-fold, whereas IGF-1 did not affect DNA repair by NHEJ. IGF-1R enhancement of HRR correlated with the translocation of Rad51 to foci of DNA damage. Inhibition of Rad51 expression by short interfering RNA (siRNA) experiments markedly decreased % of MMC positive for Rad51 nuclear foci and increased hyperglycemic DNA damage. We conclude the activated IGF-1R rescues mesangial cells from hyperglycemia-induced danger signals that target genomic DNA, by suppressing ROS and enhancing DNA repair by HRR.