This paper presents a rapid protocol of microwave-assisted green synthesis of non-oxidized metallic copper nanoparticles (CuNPs) using green tea (Camellia sinensis (L.) Kuntze) extract. Following the successful biosynthesis, characterization techniques such as UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) associated with Energy Dispersive X-ray analysis (EDX), X-ray Diffraction (XRD) and Zeta analysis were employed to confirm the presence of metallic CuNPs and reveal their morphology. UV-vis spectrum of fabricated CuNPs indicated its characteristic maximum absorbance at 570 nm. Synthesized CuNPs were found to be round to globular in shape, with average size of 45.30 nm, and showed excellent stability without any aggregation for several months. EDX graph confirmed the highest amount of copper atoms (77.96%) along with carbon and oxygen with the percentage of 17.17% and 4.87%, respectively. The non-toxic nature of the phytosynthesized CuNPs was further established by using healthy mouse fibroblast L929 cell line, which showed their potentiality for biological research and many other applications.