Zinc oxide (ZnO) was biosynthesised from aloe vera plant extract. The aloe vera plant extract was used as a reducing agent in biosynthesis process. Green synthesis method was proposed because it is cost effective and environmentally friendly. ZnO was characterised using SEM, EDX, FTIR, and XRD analyses. The antibacterial property was tested against Escherichia coli. The effects of aloe vera volume (2-50) mL, precursor concentration (0.001-0.300) M, reaction time (20 min-48 h), and temperature of the reaction (26-200) °C on ZnO characteristics were investigated and screened using a two-level factorial method. Based on the observation and ANOVA analysis result, precursor concentration was the only significant parameter that affected the production of the ZnO nanoparticles (NPs). The EDX analysis proved the presence of ZnO while the SEM analysis confirmed the average size of ZnO particle size was in the range of (18-618) μm with a rod-shape appearance. The XRD analysis showed that the average crystallite size was 0.452 μm and it was in the hexagonal phase. It was also proven to have antibacterial property against E. coli.