The aim of this study is to develop composites with high thermal conductivity by employing the thermophysical properties of aluminum nitride (AlN), hexagonal boron nitride (hBN), and synthetic graphite (SG). AlN, hBN, and SG filled polyamide 6 (PA) composites were prepared using a co-rotating twin-screw extruder and injection molding. Changes in thermal, mechanical, and electrical properties of the composites were investigated. The highest in-plane and through-plane thermal conductivity values were obtained with 50 wt.% SG and 50 wt.% AlN loadings, respectively. Mechanical strength of PA decreased for all filler loadings. Electrical conductivity results showed that AlN and hBN filled PA composites behave as electrical insulators. On the contrary, SG loading led to electrically conductive PA composites.