In this research, antagonistic activities of 30 Bacillus species isolated from various fish samples were studied. Isolated Bacillus species were analyzed using the agar diffusion method in terms of their general inhibition effects against some food pathogen/contaminant bacteria and lactic acid bacteria isolated from the fish intestinal tracts. Some of these strains exhibited antimicrobial activity against Bacillus subtilis, Pseudomonas fluorescens, Lactobacillus coryneformis, Lactobacillus plantarum and Lactobacillus xylosus. Furthermore, the inhibitory effects of the lactic acid bacteria on the Bacillus isolates were analyzed by using the same method. It was determined that the lactic acid bacteria inhibited Bacillus spp. strains at different levels of inhibition zones