Plant-mediated synthesis of ZnO Nanoparticles (NPs) have multiple advantages over conventional synthetic methods like easy, inexpensive, eco-friendly, nontoxic by-products and no critical conditions of temperature and pressure required. In this study, 9.1 g ZnO NPs were synthesized from 230 mL of 0.2 M Zinc acetate dihydrate and 100 mL of green tea leaves extract at room temperature (25°C). The leaves extract was prepared by heating 10gm dried leaves in 100 mL of deionized distilled water at 80°C for 2 h. The synthesized ZnO NPs were dried at 40°C for 24 h and calcined at 100°C for 1 h. The agar well diffusion method was used to evaluate ZnO NPs for antimicrobial activity of selected pathogenic strains. A clear zo“ne of inhibition was measured; 40.05 mm ± 0.137 for Staphylococcus aureus, 36.15 mm ± 0.304 for Escherichia coli and 40.10 mm ± 0.050 for Aspergillus niger that were comparably better results than standard antibiotic Gentamycin that showed 25 and 26 mm zone of inhibition for Staphylococcus aureus and Escherichia coli respectively. The minimum inhibitory concentration scored as 9.765µg ± 0.00, 9.531µg ± 0.00 and 5000µg ± 0.00 for Staphylococcus aureus, Escherichia Coli and Aspergillus niger respectively, was documented low concentration than reported so far concentrations of green tea ZnO NPs.