Spinel ferrite nanoparticles with chemical equation Ni_xCu_0.1Zn_0.9xFe₂O₄(x= 0.5, 0.6, 0.7) have been synthsized using co-precipitation method followed by heat treatm ent at a temperature of 200^oC for 2h. The results of XRD, FE-SEM and VSM studies are reported. XRD patterns confirm the formation of cubic spinel phase of ferrite samples along with small amount of secondary phase of α-Fe₂O₃ whose concentration decreases as Ni²⁺concentration increases. The crystallite sizes ( in the range of 7.5-13.9 nm ) increase and the lattice parameter decreases with increase in Ni²⁺ion concentration. These values are comparable to those of NiZn ferrite without Cu substitution. It has been observed that there is a considerable reduction in saturation magnetisation ( M_s). This and differences in other magnetic parameters are attributed to considerable hanges in cation dis tribution or core shell interactions of NiZn ferrite with 10mole% Cu substitution in the place of Zn..