Nanosize nickel ferrite was synthesized by the sol–gel autocombustion method. The surface of nickel ferrite was modified by copper sulphide with the volume fractions from 0.2 to 0.42. For the CuS/NiFe$_{2}$O$_{4}$ composites the values of complex permittivity and permeability in the microwave range, values of conductivity at low frequencies and magnetic characteristics were investigated. Polymer composites CuS/NiFe$_{2}$O$_{4}$–polychlorotrifluoroethylene (PCTFE) were obtained by hot pressing technique. With an increase in the content of copper sulphide of polymer composites, an increase in the values of the complex dielectric constant in the microwave range of 2–3 times was observed. The values of electrical conductivity for the 0.2CuS/NiFe$_{2}$O$_{4}$–PCTFE system are 4–5 orders of magnitude lower than for the 0.42CuS/NiFe$_{2}$O$_{4}$–PCTFE system with an increase in the concentration of copper sulphide in polymer composites. The change in the ratio of the conducting and magnetic components in the studied system makes it possible composites with adjustable permittivity and permeability in the microwave range.