To optimize magnetic fluids for applications, preference is given to methods that separate the nanoparticles on the basis of their magnetic properties. Therefore, a magnetic method has been developed for the fractionation of magnetic fluids into two or more fractions. A common magnetic fluid was fractionated by this method. Magnetic and nonmagnetic properties of the fractions obtained and the original sample were measured. The magnetic method fractionates the particles in accordance with their magnetic moment and that it has good recovery as well as reproducibility. Finally, magnetic fractionation is compared with other fractionation techniques.