Background: Cardiotoxicity (CT) can be developed due to prolonged use of higher doses of some drugs, exposure to some chemicals, toxins or infectious agents and also by some disease conditions. Natural plant foods such as peanut (Arachis hypogaea L.) may have free radical scavenging activity, thereby can be used for the prevention and management of heart disease. Objective: To observe the protective effect of peanut (Arachis hypogaea L.) and its combined action with propranolol on histological changes in isoproterenol induced cardiotoxic rats. Method: This experimental study was carried out in the Department of Physiology, Sir Salimullah Medical College, Dhaka in 2012. For this purpose, 20 Wistar albino rats, age 85-100 days, weighing 120 to 150g (initial body weight) were included in the peanut treated group. They were sub-divided into CT-ISO-P (Cardiotoxic group with isoproterenol after peanut treatment) and CT-ISO-C (Cardiotoxic group with isoproterenol after combined treatment of peanut and propranolol). Age and weight matched 30 Wistar albino rats without any peanut supplementation were taken and sub-divided into three sub-groups, BC (Baseline control), CT-ISO (Cardiotoxic group with isoproterenol) and CT-ISO-PRO (Cardiotoxic group with isoproterenol after propranolol treatment). Each sub-group consisted of 10 rats. After taking final body weight all the rats were sacrificed on 22 nd day. The heart was removed and preserved in 10% formalin for histological processing. To find out the histopathological changes of heart tissue, histological slides were prepared and were observed under microscope in the Department of Pathology, SSMC. Histological findings were categorized by scoring as mild, moderate and severe histological changes. The statistical analysis was done by one way ANOVA and Bonferroni test as applicable. Result: In this study, percent change from initial body weight to final body weight was significantly (p<0.01) lower both in CT-ISO-P and CT-ISO-C as compared to that of BC. Again, histological score was significantly (p<0.01) higher in CT-ISO in comparison to that of BC. Moreover, these scores were significantly lower in CT-ISO-PRO (p<0.01), CT-ISO-P (p<0.05) and CT-ISO-C (p<0.05) in comparison to that of CT-ISO. Similarly, this score was significantly (p<0.01) lower in CT-ISO-C when compared to that of CT-ISO-P. Conclusion: The present study revealed that peanut can preserve almost normal histological architecture of heart tissue in isoproterenol induced cardiotoxic rats. However, the combined therapy of peanut with propranolol showed synergistic effect on preventing histological changes in heart tissue.