Aim To investigate the role of leptin-p38 mitogen-acrivated protein kinase （MAPK） pathway in high glucose （HG）-induced injury in H9c2 cardiac cells. Methods H9c2 cardiac cells were treated with HG to establish a model of cellular injury induced by HG. Cell viability was tested by cell counter kit 8 （CCK-8）. The intracellular level of reactive oxygen species （ROS） was measured by dichlorfluorescein staining and photofluorography. The changes in morphology and amount of apoptotic cells were tested by Hoechst 33258 nuclear staining. Mitochondrial membrane potential （MMP） was detected by rhodamine 123 （Rh123） staining followed by photofluorography. The expression levels of leptin and p38MAPK protein were measured by Western blot assay. Results Exposure of H9c2 cardiac cells to 35 mmol/L glucose （HG） markedly enhanced the expression of leptin. Pretreatment of cells with 50 μg/L leptin antagonist （LA） for 24 h before exposure to HG significantly inhibited HG-induced upregulation of phosphorylated p-p38MAPK expression. Pretreatment of H9c2 cardiac cells with either LA for 24 h or SB203580 （an inhibitor of p38MAPK） for 60 min prior to exposure to HG reduced HG-induced injuries, as evidenced by an increase in cell viability, decreases in apoptotic cells, ROS production and dissipation of MMP. Conclusion The leptin-p38MAPK pathway is involved in HG-induced cardiomyocyte injury.