Powdery mildew, caused by Blumeria graminis f. sp. tritici, is an important disease of bread wheat (Triticum aestivum L.) in many countries worldwide, including Egypt. Powdery mildew infects all parts of wheat plants that negatively affect grain yield and therefore caused economic loss. Some microorganisms i.e. Bacillus subtilis, B. chitinospora, B. pumilus and yeast (Rhodotarula sp.) were used in the current study as biocontrol agents (BCAs) for controlling powdery mildew in wheat variety (Sakha93), under field conditions, compared to the recommended synthetic fungicide; Tilt. The superior and best treatments decreasing infection type (IT), disease severity (%), and increasing 1000 kernel weight and grain yield per plot. Application of B. subtilis and B. chitinospora, were compared to the other treatments and the tested fungicide. Scanning electron microscopy studies confirmed the superiority of the aforementioned two biocontrol agents (BCAs), as application of each, minimized suppressed mycelial growth and collapsed the spores of the causal pathogen. Application of B. chitinosporain, particular, suppressed the conidial germination, caused a rupture, and deformation of germ tube. Also, both mycelia and conidiospores became shrinking on the surface of the treated wheat leaves. Extracts of the four microorganisms used in this study interacted directly with Blumeria graminis, and this antifungal effect was responsible for the observed disease protection. The obtained results in this investigation gave an evidence to the possible use of such microorganisms as safe and effective alternatives for controlling powdery mildew disease of wheat under field conditions.