The purpose of this study was to explore the mitigating effect of morphine on the myocardial ischemia-reperfusion injury (MIRI) in rats through the cyclic adenosine monophosphate/protein kinase A (cAMP/PKA) pathway. A total of 30 male Wistar rats were assigned into sham group, MIRI group and morphine group using a random number table. The model of MIRI was routinely established. Then, the pathological changes in the morphology of myocardial tissues were observed via hematoxylin-eosin (HE) staining. The levels of the oxidative stress indicators superoxide dismutase (SOD) and malondialdehyde (MDA), the content of the inflammatory cytokine tumor necrosis factor alpha (TNF-α), interleukin-1 beta (IL-1β) and IL-6 and the quantity of glutathione peroxidase (GSH-Px), lactate dehydrogenase (LDH), creatine kinase (CK), CK-MB and cardiac troponin I (cTnI) in the myocardial enzyme spectrum were determined and analyzed through enzyme-linked immunosorbent assay (ELISA). Moreover, the messenger ribonucleic acid (mRNA) and protein expressions of cAMP, PKA, cAMP-response element binding protein (CREB) and phosphorylated CREB (p-CREB) in the cAMP/PKA signaling pathway in the myocardial tissues were measured using real-time polymerase chain reaction (PCR) and Western blotting, respectively. The results manifested that compared with those in MIRI group, the levels of myocardial infarct size, LDH, CK, CK-MB, cTnI, MDA, TNF-α, IL-1β, IL-6 and p-CREB were decreased, while the levels of GSH-Px, SOD, PKA and CREB were increased in the morphine group. In conclusion, morphine may mitigate MIRI in rats through the cAMP/PKA signaling pathway.