Abstract: Green synthesis of nanoparticles has emerged as an eco-friendly and sustainable approach in nanotechnology. In the present study, copper nanoparticles (CuNPs) were synthesized using Murraya koenigii (curry leaves) extract as a natural reducing and stabilizing agent. The phytochemicals present in the curry leaves, such as flavonoids, phenolic compounds, alkaloids, and terpenoids, play a crucial role in the bioreduction of copper ions (Cu²⁺) into copper nanoparticles and also prevent their aggregation by acting as capping agents.The synthesis process was indicated by a visible color change from blue to dark brown, confirming the formation of CuNPs. The synthesized nanoparticles were characterized using advanced analytical techniques such as Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Fourier Transform Infrared Spectroscopy (FTIR). SEM analysis revealed the surface morphology of nanoparticles, while TEM provided detailed information about particle size and shape, showing that the particles were predominantly spherical and within the nanoscale range. FTIR analysis confirmed the presence of various functional groups associated with plant biomolecules, indicating their involvement in reduction and stabilization processes.Furthermore, the catalytic activity of the synthesized CuNPs was evaluated using the reduction of 4-nitrophenol to 4-aminophenol in the presence of sodium borohydride (NaBH₄). The nanoparticles exhibited excellent catalytic efficiency due to their high surface area and active sites.This study demonstrates a simple, cost-effective, and environmentally friendly method for the synthesis of copper nanoparticles with significant catalytic applications. The findings highlight the potential of plant-mediated nanoparticles in green chemistry and environmental remediation.