The present investigation deals with the synthesis and characterization of Ce–Ni ions substituted nanocrystalline strontium–barium hexaferrites (Sr 0.5Ba 0.5Fe 12O 19) by the chemical co-precipitation method, with focus on the optimization of annealing temperature for the hexagonal phase development. The synthesis involves co-precipitation of aqueous solutions of water-soluble salts of strontium, barium and iron, at pH 9 using an ammonium hydroxide solution as a precipitating agent. The optimum temperature of annealing, necessary for the hexagonal phase development, is determined on the basis of thermo-gravimetric analysis (TGA). The co-precipitate is annealed at a temperature of 1323 K for 6 h, to produce a single magnetoplumbite phase of Sr–Ba hexaferrites, with the corresponding average crystallite size ranging from 36 to 48 nm. Observed changes in the lattice structure determined by the powder X-ray diffraction (XRD) studies are not in contradiction with the results of TGA. DC-electrical resistivity increases from 1.8 × 10 10 to 12.5 × 10 10 Ω cm, whereas the drift mobility, dielectric constant and dielectric loss tangent decrease with increasing the Ce–Ni content of the samples. Material of above-mentioned characteristics is considered to be suitable for applications in the microwave and surface mount devices (SMD) for fabricating the multilayer chip inductors (MLCI).