This thesis investigated the effect of cellular morphologies on mechanical properties of Thermoplastic Polyolefm (TPO) cellular foams. Cellular closed-cell TPO foams were prepared using a two-stage batch method and injection molding process. The microstructure of these foamed samples was controlled by carefully altering the processing parameters of two different foaming processes. The foam morphologies were characterized in terms of the cell density, foam density and average cell size. Tensile properties, elastic recovery and impact resistance of various foamed TPO samples were correlated with different foam morphologies. This research is summarized in three major findings:​ 1) The weight reduced TPO can be achieved without sacrificing much of the mechanical strength by introducing cellular structure in the materials, 2) the elastic recovery of the TPO can be significantly improved by the cellular structure in the materials and (3) the impact resistance of the TPO foams is significantly reduced by the cellular structure in the materials.