The present paper report a study of the nickel doped cobalt ferrite Co 0.9 Ni 0.1 Fe 2 O 4 have been synthesized by conventional hydrothermal technique followed by microwave sintering. The Co 0.9 Ni 0.1 Fe 2 O 4 nanoparticles are characterized by X-ray diffraction (XRD), transmission electron microscopy, field emission scanning electron microscopy, particle size analyzer and vibrating sample magnetometer. The XRD spectra show a high degree of crystallinity and also indicates that the diffraction peaks correspond to the cubic spinel structure. Transmission electron microscopy indicating that, the crystallite size of Co 0.9 Ni 0.1 Fe 2 O 4 nanoparticles was in the range of 40–75 nm. The nanoparticles show relatively high saturation magnetization of 32.540 emu/g.