We aim to explore various effects of doses of Jatropha mollissima against isoproterenol-induced myocardial infarction in the rat. Rats were divided into 6 groups (10 rats in each). Group-1 was normal to control, and Group-2 was considered intoxicated isoproterenol (ISP) (100 mg/kg, s. c.) Group-3 was treated with standard drug carvedilol, while Group-4, 5, and 6 were treatment groups and treated with J. mollissima extract at the doses of 400, 600, and 800 mg/kg, respectively. Preliminary phytochemistry, histopathological variation in the myocardium, antioxidant potential, and cardiac biomarkers (serum glutamic oxaloacetic transaminase, triglyceride, 2,4,6-trinitrotoluene, serum glutamic pyruvic transaminase, lactate dehydrogenase, and creatine kinase muscle–brain fraction), cardiac rate, electrocardiographing, and pressurization rate index were estimated. This study indicates that the extract proved to have cardioprotective potential and significantly reduced the cardiac biomarkers in a dose-dependent fashion because of flavonoid contents and antioxidant property. The histopathological analysis shows marked improvement in J. mollissima groups handled in comparison with ISP. The present evaluation suggests that J. mollissima has exceptional cardioprotective potential contrary to toxicity caused by isoproterenol. We recommend further studies at the molecular level to frame the exact mechanism of action.