Our work aims to elucidate the effect how microRNA‐148b (miR‐148b) participated in myocardial ischemia/reperfusion (I/R) injury via regulation of Wnt/β‐catenin signaling pathway. The in vivo myocardial I/R models of SD rats and in vitro hypoxia/reoxygenation (H/R) models of H9C2 cells were established. The heart function and infarction area of rats and lactic dehydrogenase (LDH), creatine kinase (CK), malondialdehyde (MDA), and superoxide dismutase (SOD) levels were evaluated. Myocardial cell viability was measured using positron emission tomography combined with computer tomography and (3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide) assay, and the apoptosis was assessed by terminal deoxynucleotidyl transferase‐mediated nick‐end labeling method and flow cytometry; quantitative reverse‐transcription polymerase chain reaction and western blot were used to detect the related molecules expressions. The myocardial infarction area of rats was significantly increased with reductions in LVSP, + dp/dtmax, − dp/dtmax, LVFS%, LVEF% and standardized uptake value and elevation in left ventricular developed pressure after ischemia/reperfusion (I/R), and the LDH, CK, and MDA levels were enhanced with the decreased SOD. The apoptotic rates were higher in I/R rats and H/R H9C2 cells with upregulated miR‐148b and cleaved caspase‐3, but decreased Bcl‐2/Bax ratio; and meanwhile, the Wnt/β‐catenin pathway was inhibited. Additionally, the H/R‐induced H9C2 cells also exhibited decreased cell viability. MiR‐148b overexpression further aggravated I/R injury of rats, whereas inhibition of miR‐148b reduced I/R and H/R injury through activation of Wnt/β‐catenin pathway. In addition, Wnt‐1 small interfering RNA exposure abolished the effect of miR‐148b inhibitor on H/R injury of H9C2 cells. Inhibition of miR‐148b improved the antioxidative ability and myocardial cell survival to suppress its apoptosis by activating Wnt/β‐catenin signaling pathway, thus ameliorating the myocardial I/R injury. Inhibition of miR‐148b can elevate the antioxidative ability, suppress myocardial cell apoptosis, promote cell viability, and reduce the myocardial infarction area through targeted activation of Wnt/β‐catenin signaling pathway, thereby mitigating the myocardial I/R injury.