Aims: To investigate the effect of antagonistic yeast Pichia membranaefaciens on alleviating oxidative stress caused by Penicillium expansum in sweet cherry fruit. Methods and Results: At two maturity stages of sweet cherry fruit, P. membranaefaciens restrained blue mold rot caused by Pe. expansum. There was not any decay in yeast-treated fruit even at 5 days after inoculation. Carbonylated proteins accumulated to a lesser extent in yeast-treated fruit than in control fruit, particularly in non-full-matured stage fruit. Higher activities of catalase (CAT) and glutathione peroxidase (GPX) were observed in yeast-treated fruit, which consisted of the transcript expressions of CAT and GPX genes. In addition, yeast treatment also stimulated the transcript expression of Gns1 and activity of b-1,3-glucanase. Conclusion: Induction of antioxidant defence response may be an important mechanism of antagonistic yeast in mitigating pathogen-induced oxidative stress to postharvest fruit and controlling postharvest disease. Significance and Impact of the Study: The results of this study showed a potential mode of action of antagonistic yeast in postharvest fruit disease control, which may be an important development in the understanding of antagonists in postharvest biocontrol and may provide important guidance for their application in the future.