Erysiphe necator is a destructive fungal pathogen that compromises grapevine yield and quality, leading to substantial economic losses. Therefore, elucidating host resistance mechanisms is essential. In this study, we identified an ethylene response factor, VqERF1B, that exhibits sustained high expression during E. necator infection in Chinese wild grape Vitis quinquangularis accession ‘Danfeng-2’. Transient overexpression of VqERF1B in grape leaves enhanced resistance to E. necator by elevating transcript levels of pathogenesis-related (PR) genes, including PR1, PR2, PR5, and PR10. Conversely, silencing VqERF1B resulted in increased susceptibility. Moreover, transgenic Arabidopsis lines stably overexpressing VqERF1B exhibited enhanced resistance to powdery mildew, associated with elevated PR gene expression and increased accumulation of reactive oxygen species (ROS). A series of assays identified VqMAPK3, a phosphorylated mitogen-activated protein kinase, as a direct interactor of VqERF1B. Furthermore, VqERF1B was shown to bind directly to the promoters of VqPRs, thereby activating their transcription. Notably, the VqMAPK3-VqERF1B complex exhibited greater transactivation activity on VqPR promoters than VqERF1B alone, indicating that VqMAPK3 positively modulates VqERF1B-mediated transcription of PR genes. This work advances understanding of the molecular basis of grape resistance to E. necator and provides a foundation for molecular breeding strategies.