Green synthesis of nanoparticles has been drawn a lot of attention for many researchers, in terms of using eco-friendly resources. Green tea (Camellia sinensis L.) has been found to have abundant amount of polyphenols that may favor the green synthesis of ZnO-NPs due to its bio-reduction mechanism. The aim of this research was to utilize dried green tea and used green tea extracts to synthesize zinc oxide nanoparticles. Dried green tea leaves and used green tea leaves were extracted using different ratio of water to ethanol. The extracts were analyzed for amount of dry matter, total phenolic content, and total flavonoid content to evaluate the effect of solvent polarity. All of the extracts were used for the synthesis of zinc oxide nanoparticles, and then further analyzed for the yield and free radical scavenging activity. ZnO-NPs synthesized from dried green tea extracts using pure ethanol yielded the highest amount of ZnO-NPs (3.5651±0.0521 gram) and possessed the highest free radical scavenging activity (9.740±0.46 %/mg) with size approximately 116.7 nm. After treated with calcination at 100°C, the free radical scavenging activity of ZnO-NPs was 13.63±1.18%/mg with size approximately 162.2 nm.