In this study, the changes of superoxide dismutase (SOD) and catalase (CAT) activities and malondialdehyde (MDA) levels in brain, muscle, liver and gill tissues of Cyprinus ccupio was determined by addition of 0.5 mg/l cyanide into the environment of fish. The fish were exposed to cyanide for 24 and 72 h. As a result of the 24-h exposure, a significant decrease observed in MDA level in muscle and in SOD and CAT activities in brain compared to the control groups. As a result of 72-hour exposure, SOD enzyme activity and MDA levels in brain tissue were increased significantly. The CAT activity in liver was remarkably higher than other tissues of C. carpio. After the exposure, some tissues increased their enzyme activities as a reaction to sodium cyanide while some other tissues were adversely affected. Consequently, we can say that cyanide presence changes the activities of SOD, CAT antioxidant enzymes and MDA levels working as indicators of oxidative stress.