Porous polyaniline (PANI)-coated multi-walled carbon nanotube (MWNT) core/shell nanohybrids were fabricated through in situ polymerization and subsequently assembled into macroscopic composites. N 2 adsorption/desorption analysis indicated that the volume of nanopores increased significantly, which could make a significant contribution to phonon scattering. Thermal annealing was also carried out to improve the Seebeck coefficient of the as-produced nanocomposites. The optimal sample showed electrical conductivity of 14.1Scm 1, a Seebeck coefficient of 79.8μV K 1 and thermal conductivity of 0.27WmK 1, resulting in a highest figure of merit (ZT) of 0.01 at a very low loading of MWNTs (<1wt%). These results will provide a potential direction to enhance thermoelectric performance of organic materials and also facilitate the application of organic materials in thermal energy harvesting or cooling.