Iron oxide nanoparticles (IONPs), because of their superparamagnetic characteristics, are of considerable interest in nanotechnology related fields including biomedical, environmental, industrial applications. however, the knowledge of IONPs toxicity is very limited especially in vivo studies. Quercetin (QT); a natural flavonoid , strong antioxidant , free radical scavenger and iron chelator, has multiple therapeutic effects. The present study aimed to explore role of IONPs and QT in rat body weight and possible protective effect of QT in chelating iron preventing fenton reaction. Twenty five male adult rats were allocated equally into five groups: control, IONPs (50 mg/kg b.w i.p. 3 times/week), QT (25 mg/kg b.w. daily per os)+IONPs, QT (50 mg/kg b.w. daily per os) + IONPs, QT (100 mg/kg b.w. daily per os) + IONPs. Rat body weights were assessed weekly till end of the study. after the 30 days brain tissues were collected for measurement of iron level. IONPs induced a non-significant difference in all weeks except at day of sacrifice there was a significant increment in body weight. Compared to IONPs group, QT 25, 50 and 100 mg/kg b.w.+IONPs induced a non-significant difference in body weight in all weeks. IONPs induced a significant increment in Fe level. Compared to IONPs group, QT 25, 50 and 100 mg/kg+IONPs induced a non-significant reduction in Fe level. the results of this study showed role of IONPs and quercetin in body weight gain and suggested protective role of quercetin in chelating Fe preventing fenton reaction occurred from its increase by IONPs.