Grapevine trunk diseases (GTDs), such as Esca and Botryosphaeria dieback, markedly impact the worldwide wine grape and table grape industry. Detection and development of antagonistic microorganisms, particularly bacteria, to achieve biological control of GTDs would be of prime importance as a future innovative alternative practice in viticulture. The antagonistic activity of 46 bacterial strains isolated from Bordeaux vineyards were evaluated against P. chlamydospora and N. parvum, two of the major pathogenic fungi involved in GTDs. Different bioassays performed under greenhouse conditions with foliar grapevine stem cuttings have shown that the efficacy of protection by the antagonistic strains significantly depended on the bacterial strain, the targeted pathogen and, for N. parvum, also on the application mode of the bacterial strain.A significant reduction in length of necrosis due to P. chlamydospora and/or N. parvum, ranging between 40 and 64% in non-grafted vine cuttings, resulted from three bacterial strains: Pantoea agglomerans (S1), Paenibacillus sp. (S19) and Bacillus pumilus (S32). Their efficacy was not dependent on application method; co-inoculation, prevention in the wood and soil inoculation for P. chlamydospora. In the contrary, preventive application of the bacteria in the wood was the method the most efficient. These strains were thoroughly further investigated to determine their major modes of action by i) Antibiosis ii) production of antifungal volatile organic compounds, which have been identified, and/or iii) induction of grapevine systemic resistance. The volatile compounds secreted by these strains were identified by gas chromatography/mass spectroscopy (GC/MS). Finally, the induction of grapevine systemic resistance was studied by the quantification of. the expression of 10 major grapevine defense genes by real-time polymerase chain reaction.< Réduire