In this work, nano-imidacloprid was prepared by direct encapsulation with ABA triblock linear dendritic copolymers composed of poly(citric acid) (PCA) as A block and poly(ethylene glycol) (PEG) as B block. Nanocapsules of imidacloprid were characterized using spectroscopy, microscopy and thermal analysis. The encapsulation process was performed by self-assembly of PCA–PEG–PCA in the presence of imidacloprid in different solvents. Comparison of the TEM images of nano-imidacloprid prepared in ethanol and water showed that, during the first day, self-assemblies appeared as small particles with an average size of 10–20 nm. Depending upon the type of solvent, the time and concentration, morphology and size of the nano-imidacloprid varied from fiber-like to globular to tubular from 10 nm to several mm in size. Higher loading capacity and slower release rate of imidacloprid from nano-imidacloprid at optimum pH of Glyphodes pyloalis׳s gut (pH=10) compared to neutral pH confirmed the selective and controllable action of nano-imidacloprid. Results of bioassays on the model insect showed that by using the nanoform of imidacloprid, essential dosage of pesticide and environmental risk decreased significantly and indicated good performance for this formulation.