This study presents a green and sustainable approach for synthesizing zinc oxide nanoparticles (ZnO-NPs) using Melia azedarach leaf extract as a reducing and stabilizing agent, with zinc acetate as the precursor. The synthesized nanoparticles were thoroughly characterized to assess their structural, morphological, and physicochemical properties, revealing nanoscale dimensions, enhanced crystallinity, and improved stability compared to commercial ZnO. Controlled release experiments under plant-relevant pH conditions demonstrated a gradual and sustained release of Zn²⁺ ions, accompanied by buffering effects and re-precipitation of Zn(OH)₂, highlighting their potential for long-term nutrient availability in soil systems. Unlike conventional studies that focus mainly on synthesis or characterization, this work emphasizes the functional performance of ZnO-NPs as nanofertilizers, combining eco-friendly production with practical agricultural applications. The plant-mediated synthesis yielded nanoparticles with uniform size distribution, enhanced dispersion, and stability, which are critical for efficient nutrient delivery and persistence in soil. Overall, this study provides a cost-effective, scalable, and environmentally benign strategy for producing ZnO nanoparticles and offers valuable insights into the development of sustainable nanofertilizers aimed at improving crop nutrition, soil fertility, and agricultural productivity.