A simple fabrication method is demonstrated for surface-enhanced Raman scattering (SERS)-active plasmonic nanoballs, which consisted of Au nanoparticles (NPs) and core-shell polystyrene and amino-terminated poly(butadiene) particles, by heterocoagulation and Au NP diffusion. The amount of Au NPs introduced into the core-shell particles increases with the concentration of Au NPs added to the aqueous dispersion of the core-shell particles. When the amount of Au NPs increases, closely packed, three-dimensionally arranged and close-packed Au NPs arrays are formed in the shells. Strong SERS signals from para-mercaptophenol adsorbed onto composite particles with multilayered Au NPs arrays are obtained by near-infrared (NIR) light illumination.