trichoderma has been widely studied for their biocontrol ability, but their use as biocontrol agents in agriculture is limited due to the unpredictable efficiency which is affected by biotic and abiotic factors in soil. isolates of trichoderma from embu soils were evaluated for their ability to control fusarium oxysporum f. sp. phaseoli., in vitro and promote seedling growth in the greenhouse. bioassays were run using dual cultures and diffusible compound production analysis. the trichoderma isolates significantly (p ≤ 0.01) reduced the mycelial growth of the pathogen. the principle mechanisms of niche competition, mycoparasitism, and antibiosis were observed in growth of the pathogen mycelium in the presence of trichoderma spp., through development of inhibition zones. there was coiling of hyphae around the pathogen mycelium coupled by lysising of cell wall trichoderma spp., where t. reesei and t. koningii were the most effective isolates. studies were indicative of the synergistic ability of trichoderma spp., being an effective biocontrol of bean seedlings against fusarium wilt while also promoting plant growth.