Phytosynthesized copper doped cerium oxide nanoparticles (NPs) are synthesised and their application potential in antibacterial activity is investigated. The compensative effect of Cu²⁺ occupying Ce^4+/Ce³⁺ site and redox conversion of Ce⁴⁺ to Ce³⁺ are found to facilitate the antibacterial activity of the doped NPs. The preliminary characterizations are done using X-ray diffraction, Fourier transform infra-red spectroscopy, Raman spectroscopy and energy dispersive analysis of X-rays. The particle size distribution curves from Field emission scanning data give the mean particle sizes to be ∽ 20.4 nm, 19.9 nm and 18.8 nm respectively for pure, lightly doped and heavily doped NPs. The Transmission electron microscopy manifests tetra and hexa-shaped particles, indicating the presence of Ce₂O₃/Ce_1-xCu_xO₂ along with ceria in pure and lightly doped and an additional presence of CuO in the heavily doped. The X-ray photoelectron spectra of Ce 3d deconvolute to ten peaks corresponding to Ce³⁺ and Ce⁴⁺ yielding Ce³⁺/Ce⁴⁺ % ratio <1 and Cu 2p and O1s spectra are fitted to assess variation in Cu% and oxygen vacancies with doping. The Cu doped CeO₂ samples show a commendable improvement over pure ceria, in the antibacterial activity against pathogenic bacteria Escherichia coli, Staphylococcus aureus and Bacillus Cereus.