During the cultivation of button mushrooms, the green mold epidemic, which causes a decrease in productivity, is a very important problem. The environmental harm of chemicals used in the control of such epidemics and the demand of consumers for organic products without chemicals have brought environmentally friendly biological control to the fore. Biological control can be achieved by the use of antagonistic microorganisms and their metabolites. In this study, the effectiveness of Bacillus and Pseudomonas spp. for the biological control of the green mold disease agent Trichoderma aggressivum subsp. in Agaricus bisporus cultivation was examined. For this purpose, the antifungal effects of Bacillus and Pseudomonas spp. against T. aggressivum strains were examined by an in vitro dual culture test and the agar well diffusion method. Then, it was determined whether the bacterial strains showing antifungal activity showed antagonistic activity against A. bisporus. Although none of the Pseudomonas spp. showed antifungal activity against T. aggressivum strains, most of the Bacillus spp. were found to have high activity. It has been concluded that Bacillus sp. Ö-4-82, which shows high antifungal activity against T. aggressivum subsp. and low antagonism against A. bisporus, may be potential biological control agents for button mushroom cultivation.