Cobalt Manganese Ferrite nanoparticles (Co1-xMnxFe2O4 with x varying from 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) of size varying from 16nm - 73 nm were synthesized by simple co-precipitation method. The obtained samples were characterized by X-ray diffraction analysis, Fourier Transform Infrared spectroscopy, Vibrating Sample Magnetometer. The structure of the samples was determined by using X-ray diffraction Characterization. X-ray diffraction analysis shows that the synthesized samples were cubic spinel in structure. The obtained XRD result shows that the lattice constant (ao) increased and the average crystallite size shows decrement with manganese substitution. The average crystallite size of the particles was determined by using Debye Scherrer’s Formula. Fourier transform infrared spectroscopy (FTIR) in the range 4000-400 cm-1 was reported. The water absorption bonds and the spinel structure of crystalline cobalt manganese ferrite nanoparticles were reported. The Vibrating sample magnetometer (VSM) results revealed the magnetic properties of the synthesized samples such as Remenance, Coercivity and saturation magnetization. The VSM results reported that the remenance and Coercivity were in decrement and the Saturation Magnetization found to be decrease and increase with Manganese implementation in cobalt ferrite nanoparticles. The synthesized cobalt manganese ferrite magnetic nanoparticles could be used in ferroelectric and in magnetic recording applications.