Myocardial ischemia/reperfusion (MI/R) injury is a leading cause of damage to cardiac tissues and is associated with high mortality and disability rates worldwide. Oxypaeoniflorin (OPA) has been found to be the main constituent of Paeonia veitchii Lynch. This study was conducted to explore the effect of OPA on MI/R injury and its potential mechanism. An in vivo MI/R injury model was established by transient coronary ligation in BALB/c mice, and an in vitro hypoxia/reoxygenation (H/R) injury model was established with rat cardiomyocyte H9c2 cells. Echocardiographic assessments demonstrated that OPA significantly reduced disruption of cardiac function and improved the indicators of ejection fraction (EF) and fractional shortening (FS). The enzyme-linked immunosorbent assay (ELISA) results suggested that OPA significantly reduced the release of myocardial infarction-related factors, such as the creatine kinase (CK-MB), cardiac troponin I (cTnI) and cardiac troponin T (cTnT). Additionally, hematoxylin-eosin (HandE) staining demonstrated that OPA markedly inhibited the myocardial apoptosis and necrosis caused by MI/R. Consistently, the results obtained from the cell counting kit-8 (CCK-8) and flow cytometry assays revealed that OPA obviously reversed the H/R-induced decrease in cell activity and increase in apoptosis of H9c2 cells. Furthermore, western blot assays indicated that OPA inhibited apoptosis by activating the Sirt1 (silent information regulator factor 2 related enzyme 1)/Foxo1(forkhead transcription factor FKHR) signaling pathway in myocardial tissues and H9c2 cells. Collectively, these novel findings are the first to provide strong evidence that OPA attenuates MI/R injury by activating the Sirt1 (silent information regulator factor 2 related enzyme 1)/Foxo1(forkhead transcription factor FKHR) signaling-mediated anti-apoptotic pathway.