Nanoparticle-reinforced thin films synthesis is often limited by precipitation thermodynamics and kinetics to certain material combinations and nanoparticle size distributions. We demonstrate a new method that allows direct co-deposition of mono-sized nanoparticles with various matrix materials, independent particle size and composition control, yielding flexible material selection, and nanoparticle density spatial variations laterally and depth-wise. Tungsten nanoparticles were co-deposited into magnetron-sputtered copper, giving a uniform distribution of nanoparticles in transmission electron microscopy. To demonstrate the application potential, W nanoparticles stabilized nanograined Cu at 500 °C; pure Cu reference showed significant grain growth. This method opens new possibilities in tailored nanocomposite fabrication. (nhnhanh)