Objective To observe the effect of nuclear factor‑erythroid 2‑related factor 2 (Nrf2) in diabetic rats preconditioning with resveratrol (Res) against myocardial ischemia/reperfusion injury (MI/RI). Methods Healthy adult male SD rats weighing 200‒220 g and aged from 4 to 5 months were fed with high‑fat diet for 4 weeks and then intraperitoneally injected with streptozotocin (STZ) 30 mg/kg to establish a diabetic rat model. Thirty successfully modeled rats were divided into three groups according to a random number table (n=10): a sham operation group (a Sham group), a myocardial ischemia/reperfusion group (an MI/R group) and a myocardial ischemia/reperfusion+resveratrol group (an MI/R+Res group). A rat model of MI/RI was established by ligation of the left anterior descending coronary artery for 30 min before reperfusion for 120 min. In the MI/R+Res group, 15 mg/kg Res was intraperitoneally injected 7 d before establishment of the MI/RI model, once a day for 7 consecutive days. The Sham and MI/R groups were intraperitoneally injected with an equal volume of dimethyl sulfoxide (DMSO) and PBS mixture. Left ventricular ejection fraction (LVEF) and left ventricular short axis shortening (FS) were measured by B‑mode ultrasonography. Five rats were sacrificed 120 min after reperfusion. Myocardial infarction size was measured by 2, 3, 5‑triphenyl‑2H‑tetrazolium chloride (TTC) staining. Another five rats were sacrificed to collect blood samples from the abdominal aorta for measurement of lactate dehydrogenase (LDH), a marker of myocardial injury, and creatine kinase isoenzyme (CK‑MB). Their myocardial tissues were collected to determine the levels of superoxide dismutase (SOD), malondialdehyde (MDA) and reactive oxygen species (ROS) by enzyme‑linked immunosorbent assay (ELISA). The contents of Nrf2 were observed by immunohistochemistry. The expression of Nrf2, n‑Nrf2 and heme oxygenase‑1 (HO‑1) were determined by Western blot. Results Compared with those in the Sham group, LDH, CK‑MB concentration, ROS and MDA content in the MI/R and MI/R+Res groups significantly increased while LVEF, FS, and SOD activity in the MI/R and MI/R+Res groups significantly decreased. Meanwhile, the myocardial infarction sizes in the MI/R and MI/R+Res groups were increased, and the expression of Nrf2, n‑Nrf2 and HO‑1 protein was down‑regulated (all P<0.05). Compared with those in the MI/R group, LDH, CK‑MB concentration, ROS and MDA content significantly decreased in the MI/R+Res group, while LVEF, FS and SOD activity significantly increased in the MI/R+Res group. Also, in the MI/R+Res group, the myocardial infarction size decreased while the expression of Nrf2, n‑Nrf2 and HO‑1 protein increased (all P<0.05). Conclusions Resveratrol preconditioning relieves myocardial injury in diabetic rats with ischemia/reperfusion, which may attribute to activation of Nrf2.