The effect of copper ion substitution for nickel on electrical and magnetic properties of NiFe2O4 ferrite is reported. The spinel ferrite system Ni1-xCuxFe2O4 with x=0, 0.1 and 0.2 was synthesised by standard double sintering ceramic method. X-ray diffraction study confirms the formation of single-phase nickel copper ferrites with space group of Fd3m. The investigation on dielectric constant, dielectric loss tangent and ac conductivity was carried out in the frequency range 100 Hz-1 MHz at room temperature. Dielectric constant and loss tangent were found to decrease as the frequency increases. This is attributed to the Maxwell-Wagner polarization. Temperature-dependent dc resistivity was carried out in the temperature range from 300 to 800 K. Conduction mechanism in these ferrites is discussed on the basis of electron exchange between Fe2+ and Fe3+ ions on the octahedral B-sites. The hysteresis measurements were done to determine Saturation magnetization (M-s) and coercivity (H-c) of the samples. The Cu content has a significant influence on the electromagnetic properties, such as saturation magnetization, coercivity, dielectric constant, loss tangent, dc resistivity and ac conductivity. The possible reasons that are responsible for the composition dependence of the properties were discussed. (C) 2009 Elsevier B.V. All rights reserved.