In this work the magnetic fluids based on the Ni0.5Co0.5Fe2O4 nanoparticles have been obtained by the chemical co-precipitation method. Morphological analysis, elemental composition of the Ni0.5Co0.5Fe2O4 nanoparticles and magnetization of the magnetic fluid were studied by transmission electron microscope (TEM), energy-dispersive X-ray (EDX) analysis and vibrating sample magnetometer (VSM).