Nanopesticides have been acknowledged by International Union of Pure and Applied Chemistry as a critical tool for revolutionizing future agricultural practices. However, the existing nanopesticides are often plagued by high costs, strict preparation conditions, uncontrollable size, and poor stability. Herein, taking the non‐systemic insecticide lambda‐cyhalothrin (LC) as a model pesticide, a series of LC‐loaded poly(octyl acrylate) nanogel formulations (LONFs) simultaneously featuring easy‐preparation, size‐controllable, and targeted delivery using microemulsion polymerization are developed. By adjusting the ratio of surfactants, the size of LONFs can be accurately designed to be 20, 50, 100, and 200 nm, exhibiting good stability under unconventional storage conditions (0 °C, 54 °C, ultraviolet radiation). Furthermore, reducing the particle diameter enhances the bidirectional translocation of LONFs in Vicia faba L., potentially reaching an optimal diameter (≈20 nm) for unique and rapid transport. LONFs increase the acute toxicity of LC to Aphis craccivora compared to conventional microemulsions (with a maximum reduction of 82.40% in LC50 at 24 h). Additionally, LONFs alter the lethal process of LC in human embryonic kidney 293T cells, with minimal cytotoxicity at a concentration of general application (40 mg L−1). This strategy simultaneously considers convenience, size controllability, and efficiency, providing a feasible method for the industrial development of nanopesticides.