The aim of the present study was to evaluate the protective effects of diosmin on experimentally induced myocardial infarcted rats. Diosmin (5 and 10 mg/kg body weight) was administered orally as pretreatment daily for a period of 10 days. Then isoproterenol (100 mg/kg) was injected subcutaneously into rats at an interval of 24 h for 2 days (on 11th and 12th day). Isoproterenol-induced myocardial infarcted rats showed significant changes in electrocardiogram and an increase in the levels of cardiac markers, compared with normal rats. Additionally, increased plasma lipid peroxidation products and altered lipid metabolism in the plasma were observed in the isoproterenol-induced myocardial infarcted rats. Pretreatment with diosmin (5 and 10 mg/kg body weight) minimized the electrocardiographic changes, decreased the levels of serum cardiac marker enzymes reduced plasma lipid peroxidation and minimized the alterations in the lipid metabolism of isoproterenol-induced myocardial infarcted rats. Also, diosmin inhibited the enhanced activity of liver HMG CoA reductase. The in vitro study revealed the free radical scavenging activity of diosmin. The free radical scavenging and anti-hyperlipidaemic effects are the reasons for the cardioprotective effects of diosmin.