Abstract In this work, flower shape cerium oxide (CeO 2 ) nanosheets were synthesized at room temperature through a facile precipitation method without adding any surfactant. The synthesized nanosheets were characterized by scanning electron microscope (SEM), high resolution transmission electron microscope (HRTEM), Fourier transform infrared spectroscopy (FT‐IR), X‐ray diffractometry (XRD) and X‐ray photoelectron spectroscopy (XPS). Results showed that the CeO 2 nanosheets form a petal‐like morphology and have fluorite crystal structure with no crystal phase impurity while the average crystallite size of nanosheets i. e. ~10 nm. The CeO 2 nanosheets are applied as an antimicrobial agent and the antibacterial property against G + and G − bacteria i. e. ( E. coli and S. Aureus ) were studied. The obtained results showed that the synthesized CeO 2 nanosheets had good antibacterial performance at different concentrations, which should be attributed to the reversible Ce 3+ /Ce 4+ valence states and greater oxygen vacancies. XPS study of CeO 2 nanosheets after antibacterial test confirmed the existence of Ce 3+ ions and oxygen vacancies. CeO 2 nanosheets have showed the greater potential as antibacterial nanomaterials against both the bactericides.