In vitro and in vivo studies have recently reported significant chemopreventive effects of green tea-derived polyphenols in different diseases. However, it remains unclear how such effects could be triggered. In order to elucidate the effects of epicatechin gallate (ECG) in C6 cells, both by itself and against H₂O₂-induced genotoxicity, measurements of DNA strand breaks and chromosome loss were performed. DNA damage was measured by comet and micronucleus assays. The present study shows for the first time how ECG, the major green tea-derived polyphenol, is able to exert dose-dependent genoprotective effects in an H₂O₂-induced toxicity model of C6 astroglial cells. We demonstrate that doses of ECG in a range from 0.1 to 1 μM were able to completely prevent H₂O₂-induced genotoxicity in vitro. In contrast, considerably higher concentrations of ECG (10 μM) were able to reverse previous positive effects in a dose- and time-dependent manner. The same results were confirmed by both comet (F(3,9) = 336,148; P < .001) and micronucleus (F(3,9) = 23,228; P < .001) methods. Together, our data show ECG as a dose-dependent genoprotective compound in C6 astroglial cells. This indicates that small doses of polyphenols included in our diet could have beneficial effects on neural cells, contributing to prevention of oxidative stress-associated brain pathologies. In addition, our data highlight the importance of strictly modulating doses and/or consumption of antioxidant-fortified foods or additional supplements containing such beneficial molecules.