Unique high performance thermoplastic PEEK ternary nanocomposites reinforced by nano graphitic carbon coated IF-WS₂ (inorganic fullerene-like tungsten disulphide) have been prepared and their structures have been characterised by electron microscopy imaging, electron dispersive spectrum elemental and X-ray diffraction scanning. The IF-WS₂@C–PEEK composites exhibit impressive improvements in both their mechanical and thermal properties, with an extraordinary 54% enhancement in the ultimate tensile strength at 2 wt% and a nearly 235% increase in thermal conductivity at 8 wt%. In addition, they also show an increase in decomposition temperature (over 50 °C) with higher IF-WS₂@C contents. Further investigation reveals the activation energies estimated by the Kissinger method to be 61 and 97 kJ mol⁻¹ for neat PEEK and IF-WS₂@C–PEEK, respectively. This is ascribed to the enhanced dispersion ability and better interface bonding between the PEEK matrix and IF-WS₂@C nanoparticles, which for the first time has been investigated by FTIR and XPS analysis. These significantly improved properties will no doubt expand the applications of the PEEK-based nanocomposites.