Cobalt ferrite structure besides their magnetic characteristics was studied. The citrate nitrate combustion process was utilized to prepare cobalt ferrite nanoparticles. For all prepared samples, the x-ray diffraction analysis (XRD) illustrated the single phase structure. The crystal structure has been refined using the MAUD software with the Rietveld profile method. Particle size was largely affected by the thermal processing. The formation of nanoparticles with a spherical shape has been confirmed using HRTEM technique. The magnetic nature of CoFe2O4 nanoparticles causes a degree of agglomeration which decreases the quality of the TEM images. The two characteristic bands of ferrite have been observed by FTIR analysis. The M-H curve, for the prepared nanoferrites, provided details about magnetic parameters like MS and Hc. The reduced particle size significantly reduces the saturation of magnetization, where it decreased from 99 emu/g for Co ferrite sample treated at 600oC (90 nm) to 55 emu/g for as prepared Co ferrite sample (12 nm).