In this study, we describe synthesis and characterization of zinc oxide nanoparticles from aquatic weed by a green chemistry approach. The aim of this work is to synthesize zinc oxide nanoparticles from Eichhornia crassipes leaf extract by low cost technology as against the other available technique and eco-friendly method. Aqueous leaf extract acts as a reducing and capping agent in during synthesis of nanoparticles. Formation of zinc oxide nanoparticles, optical properties, size and morphology has been analyzed by UV–vis spectrophotometer, XRD, SEM with EDX and TEM. SEM and TEM analysis show that zinc oxide nanoparticles were spherical shape and average particles size in 32±4 nm. Biological method for synthesis of zinc oxide nanoparticles using plant extracts has been suggested as a possible eco-friendly alternative to chemical and physical methods.