The zinc oxide nanoparticles (ZnO NPs) were synthesized using whole plant extracts of Caesalpinia pulcherrima in this study. Five grams of cleaned plant materials were boiled in 50 mL distilled water at 60°C for 10 min. The plant extracts were filtered through Whatman number-1 filter paper. One mM solution of Zinc nitrate hexahydrate [Zn (NO3)2.6H2O] was prepared using distilled water and used as a precursor for the synthesis of ZnO nanoparticles. Initial visual color change (yellow) was observed as a preliminary confirmation of reaction mixtures with varied time intervals. The synthesis of ZnO NPs was further confirmed using the UV- Visible absorption spectroscopy. Leaf and flower reaction mixtures exhibited strong peaks at 314 nm, stem at 305 nm, root at 299 nm and seeds at 296 nm. This green approach is safe, eco-friendly, cost-effective and the prepared nanoparticles can be used in agriculture, cosmetics and pharmaceutical industries.