In a laboratory study, the impact of crude chitinase from Aeromonas hydrophilaon the nutrient indices and on the major biochemical components of Galleria mellonellawas studied. Fourth larval instar of Galleria mellonella was treated with 135.0 U/mg protein (LC₅₀). Treatment with crude chitinase reduced the larval feeding efficiency, retarded larval growth and reduced larval weight, whereas approximate digestibility was increased. The total protein contents in the supernatant of the homogenate larvae post-treatment was decreased, as affected by crude chitinase (LC₅₀) comparing with the check treatment. A significant reduction in the total lipid content was observed and it may due to its conversion to proteins in order to compensate the reduction in protein content or to produce supplementary energy. The total carbohydrate contents were significantly reduced to be ~111.17±4.24 µg/larva with respect to the control (147.21±1.77 µg/larva). Crude chitinase from Aeromonas hydrophilamay serve as a powerful biocontrol tool against insects and provide a suitable substitute for synthetic pesticides.