Morin, a natural flavonol, exhibits antioxidative, anti‑inflammatory and anti‑apoptotic effects in various pathological and physiological processes. However, whether morin exerts a protective effect on myocardial ischemia‑reperfusion injury (MIRI) is unknown. The present study aimed to determine the effect of morin on MIRI in cultured cardiomyocytes and isolated rat hearts, and to additionally explore the underlying mechanism. The effect of morin on the viability, lactate dehydrogenase (LDH) activity and apoptosis of H9c2 cardiomyocytes subjected to hypoxia/reoxygenation, and cardiac function and infarct size of rat hearts following ischemia/reperfusion in an animal model were measured. Furthermore, the mitochondrial permeability transition pore (MPTP) opening, mitochondrial membrane potential (ΔΨm), and the change in the expression levels of B‑cell lymphoma 2 (Bcl2)‑associated X protein (Bax), Bcl‑2 and mitochondrial apoptosis‑associated proteins following MPTP opening were also detected. The results indicated that morin treatment significantly increased cell viability, decreased LDH activity and cell apoptosis, improved the recovery of cardiac function and decreased the myocardial infarct size. Furthermore, morin treatment markedly inhibited MPTP opening, prevented the decrease of ΔΨm, and decreased the expression of cytochrome c, apoptotic protease activating factor‑1, caspase‑9, caspase‑3 and the Bax/Bcl‑2 ratio. However, these beneficial effects were reversed by treatment with atractyloside, an MPTP opener. The present study demonstrated that morin may prevent MIRI by inhibiting MPTP opening and revealed the possible mechanism of the cardioprotection of morin and its acting target. It also provided an important theoretical basis for the research on drug interventions for MIRI in clinical applications.