Pulsed-laser-induced Si nanostructures on Si substrates were investigated using third harmonic Nd3+:yttrium aluminum garnet (355nm) laser irradiation under ambient conditions. Nanostructures were found in the laser-irradiated areas as well as in their surrounding areas. The laser-irradiated areas contained Si nanoparticles with an average size of about 50 nm. In the vicinity of the laser-irradiated areas, uniform nc-Si/SiOx core–shell structures were observed. Scanning electron microscopy images indicate that the core–shell structures had an average size of 500 nm while Raman data show that the Si cores were made of a large number of much smaller Si nanocrystals (nc-Si). The photoluminescence (PL) measurement of nc-Si/SiOx core–shells exhibited a broad visible emission centered at 640 nm, which can be assigned as due to defects at the interface between nc-Si and SiOx as well as oxygen-related defects.