In this study, ZnO-GO, and ZnO-ROG nanocomposites were synthesized by the green chemistry method to study their antibacterial activity. XRD pattern and XPS confirmed that the nanocomposites successfully were synthesized. The UV-vis spectroscopy results showed the bonding between ZnO nanoparticles and GO sheets can engineer the semiconductor band gap and shift the absorption edge to longer wavelengths as compared to pure ZnO. The inhibition rate of ZnO nanoparticles, GO, and RGO sheets after 12 h of contact with E. coli were 84 %, 81 %, and 73 %, respectively. Inhibition rate for Z-1GO, Z-5GO, Z-10GO, Z-1RGO, Z-5RGO, and Z-10RGO nanocomposites were 89 %, 92 %, 94 %, 85 %, 89 %, and 91 % (under dark conditions). Enhanced inhibition rate in nanocomposites may be due to the simultaneous activation of mechanisms of dissolution of Zn2+ ions from ZnO and physical interaction between the sharp edges of GO or RGO sheets and E. coli.