Metal oxide nanoparticles (NPs) receiving a significant consideration for their probable applications in nanodevices, optoelectronics, nanosensors, nanoelectronics, catalysis and information storage. The objective of the work was to be investigate the synthesis of CuO NPs and evaluation of its characterization of CuO NPs using leaf extract of Mangifera indica. Mangifera indica leaf extract was found suitable for the copper oxide nanoparticles synthesis through biological method ambient conditions. Spherical, polydispersity of CuO NPs of particle sizes ranging from 18 to 106 nm. The average size was 52.54 nm. The formation of color changes indicates that the synthesis of CuO NPs due to plasmon resonance with the active compounds present in the Mangifera indica leaf extract. CuO NPs further confirmed by FT-IR, UV–vis spectroscopy, XRD, EDX and SEM. The functional groups confirmed that the alcohol, phenol, aromatics and alkynes have a probable adherence capacity with copper oxide, which acting as a capping agent and responsible for the bioreduction process.