In this research, various emulsions of copper-based nanoparticles were synthesized through the chemical reduction method followed by utilizing the pad–dry–cure technique as an industrial approach to manufacturing bactericidal polyethylene terephthalate (PET) substrates. Copper sulfate/copper acetate, sodium hypophosphite (SHP)/ascorbic acid, and cetyltrimethylammonium bromide were employed as salts, reducing agents, and stabilizers, respectively. Also, a spin finish oil was used for forming an emulsion. The effects of type and amount of copper salt and reductant as well as the use of resin and stabilizer were investigated concerning antibacterial activities, weight, and color changes of coated samples to find optimum formulation. Field-emission scanning electron microscope (FESEM) images, mapping/energy-dispersive spectroscopy (EDX), X-ray diffraction (XRD) pattern, Raman spectroscopy, and UV–visible spectrophotometer was proved successful in synthesis and loading of copper-based emulsions on the PET substrates. The results revealed that change of copper salt, substituting SHP with ascorbic acid, the addition of resin, and the use of surfactant yielded negligible effect, enhancing impact, reducing the influence, and improving efficacy on bactericidal characteristics of the treated samples, respectively. Based on findings, the samples coated by emulsion containing only copper sulfate/SHP and emulsion including only copper acetate were considered optimum samples indicating 100% bactericidal properties against both S. aureus and E. coli pathogenic bacteria. Despite showing bactericidal activities, it was further found that the treated samples exhibited cell toxicity toward human skin cells implying their applications in indirect contact usages. Coated samples further indicated a good washing fastness even after 20 washing cycles. This route can be considered as a facile industrially applicable method for imparting bactericidal properties to polymeric substrates. Furthermore, such emulsions can potentially be consumed as an antibacterial spin finish oil in melt-spinning to develop antibacterial textiles. Graphical Abstract: [Figure not available: see fulltext.].