Abstract: Low pesticide utilization efficiency, which leads to resource waste and environmental burden, has become a critical constraint on the sustainable development of agriculture. Conventional pesticide formulations are often limited by poor targeting, rapid photodegradation, and high risks to non-target organisms. Existing controlled-release systems largely rely on complex chemical synthesis or modification, which tends to suffer from inadequate biocompatibility and high production costs. By virtue of its functional groups, such as catechol and phenolic hydroxyl moieties, the plant-derived polyphenol tannic acid can spontaneously and orderly assemble with pesticide molecules through multiple intermolecular interactions, including hydrogen bonding, coordination, π–π stacking, and hydrophobic effects, enabling the construction of structurally tunable, stimuli-responsive nanocarriers. This system obviates the need for complex synthesis processes or chemical modification, offering advantages such as biodegradability, high biocompatibility, and facile preparation. By employing structural encapsulation, it enhances pesticide stability, improves droplet adhesion and target retention on leaf surfaces, and enables precise pesticide delivery through an environmentally responsive release mechanism. Herein, this article systematically reviews the driving forces behind tannic acid self-assembly and delineates the design strategies of self-assembly systems from three perspectives: synergy of intermolecular interactions, modular structural encapsulation, and performance enhancement tailored to specific scenarios. It also summarizes innovative applications in the management of pests, diseases, and weeds, thereby providing new insights into reducing pesticide input, improving efficacy, and advancing the sustainable development of green agrochemicals.