This study was conducted to determine the effect of Terminalia arjuna bark powder supplementation on the oxidative stress of the cardiovascular system. Isoprenaline (ISO) was administered to the rats to develop the cardiac hypertrophy and myocardial infarction (MI). Terminalia arjuna bark powder was mixed with the food powder and provided for two weeks. At the end of the experiment, all rats were sacrificed and tissue samples were collected. ISO administration in rats increased the oxidative stress markers such as malondialdehyde (MDA), nitric oxide (NO), advanced oxidation protein product (APOP), and myeloperoxidase (MPO) in plasma and heart. Terminalia arjuna bark powder lowered the MDA, NO, and AOPP concentration level in ISO administered rats. Additionally, Terminalia arjuna restored the antioxidant enzymes (catalase and SOD) activities. Gene expression of antioxidant enzymes and inflammatory markers in the heart were studied. Terminalia arjuna restored Nrf-2, HO-1, HO-2, catalase, SOD, and GPx gene expression in the heart of ISO administered rats. ISO induced increased transcription levels of inflammatory genes such as IL-1, IL-6, TNF-α, TGF-β, iNOS, and NF-κB, which were decreased by Terminalia arjuna bark powder. Histopathology was checked and hematoxylin and eosin and Sirius red staining were performed on heart sections. ISO administration resulted in mononuclear cells infiltration and collagen deposition in the heart which were lowered by Terminalia arjuna bark powder. In conclusion, this study suggests that the Terminalia arjuna bark powder alleviated the oxidative stress by restoring the antioxidant genes and prevented the increase in inflammatory markers in the heart of ISO administered rats.