Nanostructured materials are an important subject in different applications. Zinc oxide (ZnO) nanoparticles have much attention because of their unique properties. The objective of this work is to synthesis zinc oxide nanoparticles by simplest chemical method (direct aqueous precipitation). Also, the effect of zinc oxide addition to polyurethane foam (PUF) on the mechanical and sound properties has been evaluated. Different concentrations of ZnO (0.25, 0.5, 1, 2 and 3 wt.%) were used. ZnO nanoparticles were characterized by some techniques such as X-Ray diffraction, Energy dispersive X-ray spectrometry and Transmission electron microscopy analysis. Scanning electron microscope was used to describe the dispersion state of the nanoparticles in the polyurethane foam. Density of PUF increased while the particle size decreased. Finally, it was confirmed that the mechanical and acoustic properties of polyurethane nanocomposites were improved and depend on the amount of nanozinc oxide.