The present study was conducted to investigate the effects of flowers ethanol extract of Elsholtzia splendens (ESE) on the antioxidant defence system in mice with 7,12-dimethylbenz(a)anthracene (DMBA)-induced oxidative stress. The ESE was pre-administered orally to 2 groups of mice at 10 and 50mg/kg body weight (BW) for 5 weeks. Subsequently, mice with pretreatment of ESE received DMBA intragastrically at a dose of 34 mg/kg BW twice a week for 2 weeks. In DMBA alone group, biomarkers of oxidative stress (TBARS value, carbonyl content, and serum 8-OH-dG) were significantly increased. Also, the antioxidant enzymes were down-regulated. ESE significantly restored the TBARS value and carbonyl content at both doses, while a decrease in the elevated serum 8-OH-dG content was observed only at the higher dose. The DMBA-induced decreases in catalase and superoxide dismutase (SOD) activities were restored to nearly control levels by ESE. Glutathione peroxidase (GSH-px) and glutathione reductase (GR) activities, as well as the reduced glutathione (GSH)/oxidized GSH (GSSG) ratio, were significantly affected by ESE at the higher dose. These results suggest that ESE possesses antioxidant activity, which plays a protective role against DMBA-induced oxidative stress.