The effects of various doses of copper (0, 50, 150, 300, 450 mg kg-1 of soil) on the activity of catalase and total antioxidant capacity (TAC) in soil under the amaranth cultivar Aztec were evaluated in a pot experiment. The activity of catalase increased in fresh and air dry soil for all objects during the growing period of amaranth (soil sampling deadlines – June, August and October). Higher activity of catalase was observed in fresh soil samples than in air dry ones. It has been shown that increasing doses of copper applied (50, 150, 300, 450 mg kg-1) contributed to a reduction in the activity of catalase in fresh and air dry soil samples in the test months in relation to the control object. The highest catalase activity was observed in objects without the application of Cu, whereas the lowest catalase activity was effected by the highest dose of Cu. An increase in total antioxidant capacity under amaranth cultivation was caused only by the first dose of copper (50 mg kg-1). The application of increasing doses of copper, greater than 50 mg kg-1, resulted in progressive reduction of the mean value of total antioxidant capacity, which in any case was lower than the value for the control object. The mean value of total antioxidant capacity increased during the growing period, regardless of the applied dose of copper. The statistical analysis showed high significant negative correlations between a dose of Cu and the catalase activity in fresh and air dry soil samples in the test months as well as between a dose of Cu and the value of its total antioxidant capacity.