The biogenesis of nanoparticles recently gained more attention. Here, we report the biogenesis of zinc oxide (ZnO) nanoparticles using aqueous extracts of the leaves, stem, root, flowers and fruits of Croton bonplandianum Baill. at room temperature. Croton bonplandianum is an important medicinal plant used to cure many pathological conditions in the traditional systems of Indian medicines due to the presence of important and specific bioactive compounds in the plant parts of this plant. Aqueous solution of Zinc Nitrate hexahydrate [Zn(NO3)2·6H2O] was used as a precursor and the various plant extracts played as reducing agents. The formation of ZnO nanoparticles was monitored by UV-Visible spectrophotometric analysis. The leaf extract showed strong absorbance peak at 302 nm, stem and fruit at 293 nm, root at 290 nm and flowers at 305 nm.