Poly(ethylene-co-vinyl acetate)/MMT nanocomposite foams were prepared by using supercritical CO2 as solvent and blowing agent. The unique properties of supercritical CO2, gas-like diffusivity and liquid-like density, allowed it to penetrate into the platelet galleries during the soaking period and push the platelets apart by expanding of CO2 bubble during depressurization. The behavior and alignment of clay nanoparticles were explained by Gibbs-Marangoni effect and the position of clay nanoparticles was investigated by Energy-dispersive X-ray spectroscopy (EDS). It is considered that clay nanoparticles aligned at the interface between polymer matrix and CO2 gas bubble, resulted in reinforcing cell wall of nanocomposite foam. Furthermore, the dispersion of MMT in the EVA/MMT nanocomposite foams was evaluated by XRD analysis. Silicate layers were completely exfoliated and homogeneously dipersed in the EVA matrix up to 5 wt% of MMT. Structure of nanocomposite foam and structural parameters were identified by SEM analysis. Nanocomposite foams show smaller cell size and more uniform cell structure compared to pristine EVA foam because increased melt viscosity of nanocomposites hindered cell growth and exfoliated silicate layers acted as heterogeneous nucleating agents. The density of nanocomposite foams was smaller than pristine EVA foam and the foaming ratio of nanocomposite foams was larger than EVA foam because of nucleating effect by nanoclay. EVA/MMT nanocomposite foams exhibited a substantially higher compressive strength and modulus than pristine EVA foam. Especially specific modulus of EVA/MMT 5 wt% nanocomposite foam was increased by 360 % compared to pristine EVA foam. As a result, EVA/MMT nanocomposite foams had improved mechanical properties and more light weight than pristine EVA foam.