To achieve polymer-based composites for electronic packaging with high thermal conductivity, Al2O3 nanoplatelets were introduced into polytetrafluoroethylene (PTFE) matrix via a cold pressing and sintering method. The effect of mass content of the Al2O3 platelets on the morphology, mechanical properties, thermal conductivity and dielectric properties of the composites was investigated. The results revealed that the Al2O3/PTFE nanocomposites exhibited higher thermal conductivities, better thermal stabilities, enhanced mechanical properties with considerable dielectric properties. The largest thermal conductivity of the Al2O3/PTFE nanocomposites filled with 25 wt.% Al2O3 platelets was 0.461 W m -1 K -1, increased by 85% compared with that of pure PTFE. The improved thermal conductivity of Al2O3/PTFE can be attributed to the formation of effective thermal conductance network within the PTFE matrix due to the inter-connectivity of Al2O3 platelets.