Superparamagnetic iron oxide nanoparticle (SPION) coated with suitable biocompatible substances have uses in various biomedical fields, particularly in magnetic resonance imaging, tissue engineering, hyperthermia and drug delivery. In this study we have used two newly formulated SPIONs. SPIONs were coated with biodegradable polymer polylactide co glycolide (PLGA) using of the two types of surfactants-didodecyldimethylammoniumbromide (DMAB) and ±-Tocopheryl glycol succinate (TPGS) for surface modification, to extend the application potential in the field of nanomedicine. The present study focuses on the evaluation of genotoxicity if any of the two types of formulated SPIONs on human lymphocyte. Human lymphocytes were exposed to SPIONs at 11.2μg/ml concentrations of Fe in each group for 3 h at 37°C. Single-dose toxicity was tested in isolated lymphocytes using MTT assay. Uncoated SPIONs were found highly toxic while the coated ones showed significantly less cell death. In vitro genotoxicity of the formulated SPIONs showed significantly lower %tail DNA than uncoated SPIONs as detected by comet assay in lymphocytes. The results show that SPION induced genotoxicity is completely dependent on its physicochemical properties. Regulation of these properties by using different coatings could decrease toxicity. Type of surface modification primarily governed the amount of DNA damage as detected by Comet assay. The results also indicate that the coatings on the SPION were biocompatible and suitable for in vivo explorations while the free SPION were found completely unsuitable for in vivo administration. © 2016 IEEE.