This study was done on 5 groups of poultry chicks from one day up to 45 days of age. We used blue green algae as source of feed additives added to the water and ration in addition to peppermint to evaluate the protective effect of peppermint against the toxicity induced by the blue green algae. The administration of blue green algae in chicken food and water caused hepato- and cardio toxicity indicated by significant increase in liver (ALT and AST) and heart enzymes (CK and LDH) and decrease in MDA and CAT. The algae showed histopathological alterations in the liver in form of congestion in the central vein, degeneration in the hepatic cords and circumscribed areas of lymphocytic infiltrations between the hepatic cords. While it was mild in heart tissues as it showed also lymphocytic infiltration and congestion of myocardial blood vessels. The biochemical parameters were corrected except the CK and LDH. The histopathological alterations were corrected by the addition of peppermint.