The grapevine (Vitis vinifera) is susceptible to many pathogens such as Botrytis cinerea, Plasmopara viticola, Erysiphe necator, and Eutypa lata. Phytochemicals are used extensively in vineyards to reduce pathogen infections, but the appearance of pesticide-resistant pathogen strains and the need for environmental protection require the use of alternative strategies. The phytohormone ethylene is assumed to play a role in the development of disease resistance. In the present study, we have treated grapevine foliar cuttings (Cabernet Sauvignon) with ethylene-releasing ethephon. This resulted in an increase in the number of pathogenesis-related protein (CHIT4c, PIN, PGIP, and GLU) gene copies and in an enhancement of phytoalexin biosynthesis by inducing the PAL and STS genes that correlated with the accumulation of stilbenes (antimicrobial compounds). Moreover, ethephon treatment triggered the protection of grapevine detached leaves and grapevine foliar cuttings against Erysiphe necator, the causal agent of powdery mildew (64% and 70%, respectively). These studies emphasize the major role of ethylene in grapevine defense.