The present study was designed to evaluate the effect of Bacillus thuringiensis israelensis (Bti) on the immune system of the adult desert locust, Schistocerca gregaria through quantitative estimation of some physical and biochemical parameters. Locusts were enhanced by injection of a sublethal dose of bacteria into the insect hemocoel at different time intervals. Results showed variable fluctuations in the body water content, hemolymph volume, density and pH after bacterial injection. Also, drastic changes in the concentrations of hemolymph carbohydrates, lipids and proteins were recorded. The protein banding pattern of the hemolymph documented certain variables as the induction of new proteins and the vanishing of others that may retained to their contribution in the immune response towards the infection. Hemocytic examination by Transmission Electron Microscope (TEM) revealed 4 types of hemocytes; Prohemocytes (PRs), Plsamatocytes (PLs), Granular cells (GRs) and Coagulocytes (COs). Certain Pathological effects were observed in the hemocyte populations following injection including vacuolization in the cytoplasm, distortion of the cell membrane and pycnosis in the nuclei. These outcomes confirm that Btihas potential role in the suppression of the desert locust immune system and can be apply in corporation with the integrated pest management (IPM) strategies as a biocontrol agent.