Abstract: Dual-mode polymer foams have been found to perform better than conventional single-mode foams because the larger cells can substantially reduce the bulk density which the smaller cells can provide higher mechanical and physical properties. However, production of dual-mode foams often require sophisticated foaming processes such as two-stage foaming and/or complicated material systems such as dual blowing agents. In this study, we show that by controlling the location of nanoparticles in the polymer matrix, dual- and even triple-mode foam structures can be formed. By pre-coating nanoparticles such as nanoclay or carbon nanotubes (CNTs) onto the surface of polystyrene (PS) beads and then conducting batch foaming with carbon dioxide (CO2) as the blowing agent, we achieved foams with inter-connected honey-comb like structure which revealed three different cell sizes, largest cells in the PS core, medium-sized cells near the interface of the PS core and the PS/particle shell, and very small cells within the PS/CNF shell. Through the processing conditions and material selection, the foam structure and cell sizes could be tunable. The foam morphology of different PS composite foams is analyzed using the SEM. The compressive, flexural and thermal properties were also measured and compared with those of conventional PS nanocomposite foams. Keywords: Polystyrene composite, multi-mode foams, carbon nanotubes (CNTs), nanoclay, batch foaming