Regenerated cellulose (RC) films coated with copper (Cu) nanoparticles were prepared from cellulose-cuprammonium solution through coagulation in aq. NaOH and subsequent reduction in aq. NaBH4. Structure and morphology of the nanocomposite films were characterized with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM). The results established the migration of Cu2+ from the inner to the surface of the RC films during the coagulation of cellulose-cuprammonium solution and the reduction from Cu2+ to Cu0. Cu nanoparticles were found to be firmly embedded on the surface of the RC films. The RC films coated with Cu nanoparticles showed efficient antibacterial activity against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). The dramatic reduction of viable bacteria could be observed within 0.5 h of exposure, and all of the bacteria were killed within 1 h.Keywords: antibacterial; cellulose; copper nanoparticles; nanocomposite film; one-step reduction;