Grapevine cane, an abundant viticultural by-product, contains high levels of stilbenoids and therefore holds promise as a natural antifugal and antimycotoxigenic agent. Produced by a microwave-assisted hydro-ethanolic extraction process, the grapevine cane extract (GCE) was tested for its activity against three mycotoxigenic fungi F. graminearum, A. flavus, and P. expansum. Dose-response assays were performed, based on radial growth and inhibition of specific mycotoxin production. For all fungi, growth inhibition IC₅₀ values clustered between 1.0 and 5.0 g/L, while for specific toxin production, IC₅₀ were lower (≈0.5 g/L) except for patulin, which increased in a dose-dependent manner in the presence of the extract. Specific experiments were designed to highlight the effect of the extracts at various stages of the fungal life cycle (e.g., spore germination, early mycelium, and established colonies). F. graminearum spores’ germination was strongly inhibited (5.0 to 15 g/L), while for other fungi, germination was only delayed. Interestingly, antifungal and especially antimycotoxigenic effects were shown to be persistent after exposure.