Mechanical behavior of graphite-filled recycled polycarbonate/maleic anhydride grafted polyethylene [PC/PE-g-MAH (80/20)] composites prepared by melt blending was investigated. The materials were first subjected to morphological analyses using wide-angle X-ray scattering (WAXS) and scanning electron microscopy (SEM). The modifier acts as a reactive compatibilizer in the structurally heterogeneous PC/PE blends. Tensile tests showed that stiffness, strength, and ductility were markedly modified by the presence of graphite in the composites. Furthermore, an enhancement of thermal stability was observed, without any significant deterioration of the mechanical properties. The relationships among these effects and microstructural characteristics of the products obtained were also analyzed.