Rhizoctonia solani is a soil-borne pathogen which can cause damage worldwide. This fungi is destructive against a wide host range on more than 142 plant species, including many economically important agricultural and horticultural crops. The use of antagonistic microbes as biological control organisms (BCOs) is beneficial plant protecting environmentally friendly approach. Antagonistic bacterial isolates which are native in Iran are adapted to this conditions and active to prevent plant disease and decrease the virulence of pathogens. For isolation and identification of these useful bacteria, in 2016, Samples from the rhizosphere of the healthy tomato, bean and potato plants were collected. 50 isolates were purified and by the use of culturing on KB medium and Ps primers we proved that they were belonged to Pseudomonas gene. Antagonistic effect of these isolates were studied by the use of dual-culture assay against AG1-IA, AG1-IB, AG2-1, AG3, AG3-KZ17, AG4-HGI, AG6-DHT and AG7 anastomosis groups. The results of this research showed that four isolates had the most biocontrol activity against the all anastomosis groups but antagonistic effect and the power of isolates against these groups were different. In some of them like AG1-IA, antagonists prevent the formation of sclerotes and have changed the colors of all groups. To prove laboratories’ results and identification of their potential in vivo, pathogenicity effect of AG3-KZ17 on three cultivars of tomato (Mobil, Falat and Riogrand) in the presence of antagonistic agents were studied. Mobil was the most sensitive and Falat was the most resistant ones against this phytopathogenic fungi. The effects of antagonists on the growth of plants and the decrease of pathogenicity were studied. Data which obtained from this research showed that virulence was decreased 2 to 36% and the height of plants was increased 10 to 50%. The wet and dry weight of plants were studied too, that were increased in comparison with the control. Among these antagonists that were investigated, one isolate was selected as the best biocontrol agent and for gene sequencing was sent to Macrogen in South Korea. The results indicated that with the possibility of 97% this strain was belonged to P. protegens Cab57 (AP014522.1). This research introduced one beneficial bacterium as a biocontrol agent and PGPR. Complementary studies for using that on a wide range of plants and pathogens are still under investigation.