Nickel ferrite and cobalt substituted nickel ferrite were synthesized by sol-gel method using citric acid as chelating reagent. X-ray diffraction revealed the formation of nanocrystalline particles having spinel structure with space group Fd3m. FTIR spectra showed fundamental absorption bands in the range 400-1300 cm-1 , related to iron ions on both octahedral and tetrahedral sites which are typical for ferrite structure. SEM analyses confirmed that the particles are agglomerated with an average size of about 1.5 µm. The ferrite powders were pressed at 5 MPa and sintered at 1200°C for 5 h. Conductivities, impedance analyses and dielectric properties of NiFe 2 O 4 and Ni 0.7 Co 0.3 Fe 2 O 4 ceramics were investigated over the frequency range of 20 Hz to 1 MHz at room temperature. The obtained experimental results are in good agreement with the reported values.