The biochemical reactions of zebra mussels Dreissena polymorpha (Pallas, 1771) exposed to different concentrations of cadmium (Cd) in the acute period (24 and 96 hours after treatment) were studied. Four variants of experimental treatment were examined: 0 μg/L Cd (control), 10 μg/L Cd, 20 μg/L Cd and 40 μg/L Cd. Changes in the enzyme activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione (GSH) and thiobarbituric acid reactive substances (TBARS) levels were determined using ELISA kits. In D. polymorpha exposed to the three experimental concentrations of cadmium, there was a statistically significant decrease (p<0.05) in SOD enzyme activity with increasing concentration or exposure times. No change was observed in CAT enzyme activity with increasing concentrations. The decrease in the activity depending on the exposure times was not statistically significant (p>0.05). As for GPx enzyme activity, a significant increase was detected after Cd application compared to the control (p<0.05). TBARS and GSH levels increased significantly in all Cd application groups compared to the control at 24 and 96 hours. The effects of different concentrations of Cd on D. polymorpha in the acute period were associated with changes in SOD, CAT, GPx enzyme activities. TBARS and GSH levels were effective parameters in determining the oxidative damage caused by Cd.