The purpose of this work was to evaluate the effect of 2,4-dichlorophenol (2,4-DCP) and pentachlorophenol (PCP) on the activity of antioxidative system and lipid peroxidation in the leaves of reed canary grass (Phalaris arudinacea). The activity of catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPX), glutathione reductase (GR) and glutathione S-transferase (GST) as well as the content of glutathione, ascorbate and phenolic compounds were determined. An induced-increase in the APX, CAT, GPX and GR activities was stronger for PCP, while a significant increase in the GST activity was noted only for 2,4-DCP. Both compounds increased the content of phenolic compounds, oxidized and reduced glutathione as well as the content of ascorbic acid. PCP induced stronger increase in lipid peroxidation than 2,4-DCP. The observed changes revealed that chlorophenols induce oxidative stress and oxidative damage in the leaves of reed canary grass.