Abstract: In this study, the effects of Arbuscular Mycorrhizal Fungi (AMF) Glomus mosseae (Gm), Glomus fasciculatum (Gf) and Rhizobium leguminosarum biovar phaseoli (Rlp), which are the important members of rhizosphere and biological control agents, were examined on the patho-system of Sclerotinia sclerotiorum (Lib.) de Bary (Ss) and common bean. The colonization and nodulation of two biological control agents exhibited differences as a result of reciprocal interactions of these items as well as the effect of the Ss. Nodulation of Rlp particularly decreased in triple inoculation. In addition, colonization of AMF significantly decreased in treatment of Ss+AMF than control AMF. Treatments of single inoculations of AMF and Rlp isolates reduced disease severity by 10.3-24.1%. It was determined that single biological control agents inoculations were more effective than dual inoculations (AMF+Rlp). When the morphological parameters of common bean were considered, all of the morphological parameters values were decreased in treatments which present pathogen isolate. Besides this, all biological control agents increased total contents of P and N in treated plants compared to the controls.