Titanium dioxide (TiO2) or titania has demonstrated excellent potential for commercial use in various arenas, such as in the paint, in pharmaceuticals and food industry. However information on the genotoxic potential of rutile form of TiO2-NP after repeated (28 days) low dose oral exposure in major organs of the reticuloendothelial system (liver, spleen, bone marrow, lymph nodes) is not known. In this study Swiss albino male mice were gavaged TiO2-NP at sub-acute concentration (0.2, 0.4 and 0.8 mg/kg body weight) over a period of 28 days. Results revealed that TiO2-NP administered was of rutile form with mean average size of 25 nm by transmission electron microscopy. The values of PDI and Zeta potential from DLS of TiO2-NP in suspension specified that the nanomaterial was stable without much agglomeration. Chromosomal aberration assay showed that TiO2-NP was genotoxic and cytotoxic. DNA damage evaluation by comet assay confirmed that long term exposure to TiO2-NP at low concentrations can induce genotoxicity systemically in organs, such as liver, spleen, and thymus cells. Structural chromosomal aberration test from bone marrow cells revealed the clastogenicity of TiO2-NP at sub chronic low concentrations. Further in vivo studies are needed to elucidate the underlying mechanisms at the molecular level. © 2019, Archana Sharma Foundation of Calcutta.