The crosslinked polyolefin foams of poly(ethylene-co-vinyl acetate) (EVA)/olefin block copolymer (OBC)/ clay nanocomposite were prepared to examine the effect of clay on the properties of the foam. The dispersed clay reduced the foam cell size and enhanced the expansion of the foam by nucleating effect. In addition, the gel content of the foam was increased, and the mechanical properties, such as modulus, tensile strength, and elongation at break, were improved by added clay. The dispersed clay reduced the polymer chain mobility and thus the tan δ peak height at glass transition temperature decreased and the peak extended to higher temperature region. The rebound resilence, sound absorption coefficient, and the ideal rubber elasticity exhibited at rubbery plateau were also reduced by the clay dispersed in the foam because of the restricted chain mobility of the matrix polymer.