Peach fruit fly, Bactrocera zonata (Saunders) is a destructive pest of horticultural crops in Egypt. The aim of the study is to find a natural eco-friendly control bioagents of this insect. The entomopathogenic fungus, Beauveria bassiana (Bals.) infected the immature stages of this insect and viewed concentration dependent patterns. Flies were the most susceptible stage of the fungal infection. Enzymatic activity measures of B. bassiana endorsed chitinase, protease and lipase activities. Biochemical analysis of infected larvae showed increases and decreases and decreased in total proteins, carbohydrates and lipids. An extreme increase in phenoloxidase level was recorded after 24 and 48 hours from infection. Acetylcholinesterase showed a decrease after 24 hours from infection followed by an increase after 48 hours. B. bassiana could be included in IPM programs as a control agent against B. zonata.