In this study, antibacterial and electrically conductive polyacrylonitrile (PAN) fibers were prepared by one‐step reaction between Cu2+ and S2– ions without extra reducing agents. The copper sulfide layer was firmly adhered to PAN fibers with the help of nitrile groups from PAN fibers and chelating agent of ethylenediaminetetraacetic acid disodium salt. The copper sulfide layer was characterized by scanning electron microscopy, transmission electron microscopy, energy‐dispersive spectrometry, X‐ray diffraction, Raman and X‐ray photoelectron spectroscopy. The results illustrated that a compact and uniform copper sulfide layer was coated on PAN fibers with 108 nm thickness, and it was proved to be a pure hexagonal phase of covellite structure. The average resistance of the resultant fibers was about 360 Ω/cm and the mass content of copper sulfide was about 13.3%. The antibacterial tests demonstrated that the resultant fibers exhibited excellent antibacterial properties with antibacterial efficiency of 99.99% against Staphylococcus aureus and 96.80% against Escherichia coli. Furthermore, the antibacterial activities and electrical conductivity still remain good after 30 cycles of standard washing, indicating their good durability when in use. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45496.