Abstract This study reports a synthesis of copper nanoparticles (CuNP) deposited on polyethylene terephthalate (PET) filters and antibacterial evaluation of the obtained filters against Escherichia coli and Salmonella enterica. CuNP were synthesized by a two-step method involving adsorption of [Cu(OH)4]2- ions onto a PET filter and subsequent chemical reduction by ascorbic acid without using other capping agents. The synthesized CuNP were 105±26 nm (mean±SD) in size and agglomerated into clusters on the PET fibres. Increasing the immersion time of the filters in [Cu(OH)4]2- solutions yielded higher amounts of deposited CuNP. SEM images and mass measurements revealed significant changes in the PET fibre surface under the alkaline medium. Passing bacterial suspensions of E. coli and S. enterica through the CuNP-deposited PET filter reduced them by 5.55 and 2.30 log values, respectively. This method of depositing CuNP onto PET material may be further developed for a wide scope of applications, not only in antibacterial filters, but also in catalytic, packaging and biomedical fields.