Biopesticides have emerged as a global trend to minimize the risks associated with synthetic agrochemicals. However, their stability and efficacies remain challenges for widespread application. Herein, co-assembled nanoparticles (AT NPs or AP NPs) based on azadirachtin (AZA) and tannic acid (TA) or phenylalanine (PA) are constructed in aqueous solution through self-assembly technology. The small particle size, low PDI, high ζ-potential, and related other physicochemical characteristics of nanoparticles can improve wettability, adhesiveness, rain erosion resistance, and photostability compared to the commercial AZA formulation. Importantly, co-assemblies with bidirectional pH-responsive disassembly in acidic or alkaline solutions, allow them to respond to microenvironmental stimuli of targets and enable controlled release of AZA. The nanosystems demonstrated remarkable in vitro and in vivo insecticidal activities against Ostrinia furnacalis and Aphis gossypii. This study illustrates a distinctive perspective for developing eco-friendly nanosystems, highlighting a water-based treatment method for biopesticides with improved physicochemical properties and utilization efficiency.