Novel thermally conductive, insulated polyimide nanocomposite films are reported here for microelectronics applications. A thermally conductive, insulated inorganic nanolayer of AlO(OH) was successfully coated onto the surface of MWCNTs, which, on the one hand, can effectively avoid the formation of MWCNT electrically conductive networks in the PI matrix and, on the other, can provide the advantage of excellent thermal conductivity properties of the MWCNTs.