In this study, vibration weld strength of polypropylene (PP) foam was investigated under various blowing ratio and welding conditions. As a result, the size of foam cell increased with increasing blowing ratio of PP foam materials, resulting in the decreased density of the PP foam materials. Furthermore, the PP foam materials provided a 68% increment of the vibration weld strength. This is attributed to the enhanced physical anchor property due to the physical impregnation into foam cell during the vibration welding. At a high blowing ratio of PP foam, the vibration weld strength tended to decrease compared to the unfoamed material.