Bacteria of the genus Bacillus are widespread in the environment, in soil and water and are part of the microbial flora of humans and animals. The reason for this is their adaptability to survival in different and even extreme conditions. Bacilli have the ability to form endospores, show their difference in physiological properties and have the ability to form numerous metabolites, several of which exhibit antimicrobial properties. The potential of B. subtilis strains in the production of secondary metabolites that mediate the antimicrobial effect has been recognized for decades. Many enzymes, antibiotics and other metabolites of different types of bacilli have medical, agricultural, pharmaceutical and other various industrial applications. There is no data in the literature on the potential of the antimicrobial effect of the Bacillus spp. metabolite on Legionella spp. and the aim of this study was to determine the antimicrobial effect of the metabolite Bacillus amyloliquefaciens on selected strains of Legionella spp. The study was conducted on L. pneumophila and L. longbeachae. The antimicrobial effect was tested by the agar well diffusion method and the double microdilution method. At the same time, the anti - adhesive effect of B. amyloliquefaciens extract and supernatant was examined. The obtained results indicate a pronounced antimicrobial potential of B. amyloliquefaciens in the supernatant, as well as its extract. Bacillus metabolites have an anti - Legionella effect and there is potential for use as biocontrol in aquatic systems.