Development of novel injection moldable materials that are thermally conductive but electrically insulative are important for the continuous advancement in modern electronics. In this context, this article details the fabrication and characterization of polymer–matrix composites (PMC), which consists of linear low-density polyethylene matrix, and filled with either silicon carbide or hexagonal boron nitride. Experimental results indicated that the addition of ceramic fillers not only promoted the PMCs’ effective thermal conductivity without compromising their electrical resistivity but also resulted in the reduction of coefficient of thermal expansion and improved mechanical properties.