Aims To investigate the efficacy and mode of action of the fatty acid-based product Foodcoat((R)) (FC) against Botrytis cinerea. Methods and Results In vitro, in vivo and field experiments were carried out to investigate the effect of different concentrations of FC on B.cinerea germination and infection of grape leaves and berries, using three selected isolates and comparing results with those achieved by the commercialized product Protector(HML) (PRT). Furthermore, the effect of field applications of FC on the grape berry microbiota was investigated. FC reduced B.cinerea germination and grape berry severity by up to 54 and 96%, respectively, compared with the untreated controls. Conclusions Foodcoat demonstrated efficacy that was equal or greater than the registered product, PRT. A multiple mode of action was hypothesized for FC suppression of B.cinerea, including: inhibition of germination and germ tube alteration, protection of host green tissues and enhancement of the natural yeast populations on the berry surface. Significance and Impact of the Study The efficacy of both products has been quantified and their modes of action described, suggesting them for field applications against B.cinerea, alone or in combined strategies. This is also the first report of a fatty acid-based product stimulating natural yeast populations on grape berries.