In this study, highly conductive nickel/copper sulfide‐polyacrylonitrile (Ni/CuS‐PAN) fibers were prepared by electroless nickel plating on CuS‐PAN fibers. The electromagnetic interference (EMI) shielding properties of the Ni/CuS‐PAN fibers were investigated as a function of nickel‐plating time. X‐ray photoelectron spectroscopy and X‐ray diffraction analyses were performed to examine the surface properties of the prepared Ni/CuS‐PAN. The surface morphology of the Ni/CuS‐PAN fibers was observed using scanning electron microscopy. The volume resistivity of the samples was measured using a four‐point probe electrical resistivity tester, and the EMI shielding effectiveness (EMI‐SE) was tested using an EMI shielding analyzer. The EMI‐SE of the Ni/CuS‐PAN fibers was significantly improved compared with those of the as‐received CuS‐PAN fibers. In addition, the EMI‐SE generally increased as the nickel‐plating time increased, with the highest EMI‐SE of the 50‐Ni/CuS‐PAN being approximately 45 dB at 2.05 GHz. The nickel layer was a key factor in determining the EMI‐SE of the Ni/CuS‐PAN fibers.