Extensive use of synthetic pesticides has negative effects on the environment and on human and animal health. Knowledge on allelopathic interactions could provide effective tools for a better exploitation of natural resources in the management of weeds without using herbicides. One of highly resistant weed species is bromus. The effects of two concentrations (0.1% and 0.2%) of Salvia sclarea L. aqueous extract on the activity of the antioxidant enzymes, superoxide dismutase (SOD) and catalase (CAT) in leaves and roots of bromus (Bromus mollis L.) seedlings, were examined. Our results showed that both concentrations of the extract used (0.1% and 0.2%) stimulated the significant increase of the superoxide dismutase activity in leaves and roots of bromus 72 hours and 120 hours after the treatment. The significant increase of the catalase activity was recorded in roots of bromus 72 h after the treatment. Two tested extract concentrations affected activity of the antioxidant enzymes in the same way, but the higher activity was observed in the roots treated with higher concentration (0.2%). The increase of the activities of antioxidant enzymes, in response to stress induced by S. sclarea aqueous extract, indicate that the plant extract possesses allelopathic activity on treated plant.