DNA damage usually happens due to the several chemical materials that induce genotoxic effect in normal cells. Cinnamon essential oil (CEO), which contains cinnamaldehyde as its major compound, has been reported to possess antioxidant activity to prevent DNA damage. The aim of this study is to evaluate the genotoxic and cytotoxic effect of CEO on doxorubicin-induced Chinese Hamster Ovary (CHO-K1) cells. The cytotoxic effect of CEO was determined by MTT assay with the parameter of IC50 while the genotoxic effect was carried out by micronucleus (MN) assay by using acridine orange fluorescent staining with the parameter of MN/1000 cells reduction number. Based on MTT assay, CEO showed cytotoxic activity with the IC50 value of 30 μg/ml and for MN assay, 3 μg/ml (1/10 IC50) of CEO decreased the percentage of micronucleus per 1000 cells up to 94,55%. Thus, the result can be summarized that CEO does not induce genotoxic and has the potency to prevent DNA damage caused by doxorubicin on CHO-K1 cells.Keywords: genotoxic, cinnamomum essential oil (CEO), micronuclei assay, in vitro