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Cyanide-induced oxidative damage may be involved in tissue lesions caused by sub-lethal cyanide poisoning. In the present study, some biomarkers of oxidative status were evaluated in liver, kidney, gill, and brain of Common Carp affected by cyanide poisoning. Moreover, possible beneficial effects of Spirulina were investigated for improvement of oxidative status and prevention of further changes. A total of 90 fish (approximately 60g) were divided into three groups, with 30 fish in each group. Group 1 served as the control. Group 2 were exposed to 0.4 mg/L potassium cyanide and received the diet without Spirulina. Fish in group 3 were fed with Spirulina (10% in the diet) in KCN (0.4 mg/L) polluted water during 30 days. The findings of the present work showed that a significant increase was observed in malondialdehyde concentrations in liver, kidney and brain of common carp following cyanide exposure. In addition, cyanide poisoning caused increment of protein carbonyls in both liver and kidney, although this increase was only significant in kidney. Supplementation of Spiulina in group 3 showed that the levels of malondialdehyde in liver, kidney, and brain effectively decreased and also it caused decrease in renal protein carbonyls to the levels that were not significantly different from control group. The findings of the present study showed that Spirulina has ameliorating effect on the KCN-induced oxidative damage in tissues of carp. Based on the present results, it can be suggested that Spirulina might have preventive effects on cyanide poisoning in carp and its dietary supplementation may have beneficial effects especially for fish species inhabiting in polluted aquatic environments.