The goal of this research was to explore if an inkjet 3D printing technology, known as Multi Jet Fusion (MJF), could be used to fabricate magnetic polymer nanocomposites with systematically varied volume fractions of magnetic nanoparticles. Soft magnetic nanoparticles were chosen because of their applications in communications technologies and other high frequency applications. However, the fabrication process described could be applied to other functional nanoparticles with, for example, conductive or dielectric properties. Magnetization and magnetic permeability were analyzed for each nanocomposite and plotted as functions of volume fraction. While magnetization, specifically saturation magnetization, has a linear relationship with the concentration of magnetic material in a composite, the relationship for permeability is not necessarily linear due to potential interactions between nanoparticles. Studying permeability as a function of volume fraction of magnetic nanoparticles in the composites allowed fitting of the data using effective medium theory mixing models. The models can then be used to make predictions about volume fraction of nanoparticles needed in a composite to achieve a specific permeability.