Wood-plastic composite (WPC) can be fine-cell processed to create a new class of low-weight composite material with improved mechanical properties that could broaden their applications. This study investigated the effects of a chemical blowing agent (CBA) and the drawdown ratio (DDR) on the surface quality, cell morphology, and mechanical properties of extruded foamed WPC profiles. The rectangular foamed WPC profiles were produced from high-density polyethylene and wood flour with different CBA contents and DDR values using a twin-screw extrusion line. The foam density, cell density, and their sizes and shapes were largely depended on the CBA content and the DDR. A foamed WPC profile with a 22% density reduction with cellular structure can be produced using an extrusion profile line.