We present a practical method for fabricating carbon nanotubes (CNTs) and conducting polymer nanocomposites with enhanced thermal stability. The conducting nanocomposites were prepared by chemical modification of CNTs with poly (styrenesulfonate) (PSS) followed by an in situ polymerization of 3,4-ethylenedioxythiophene in the presence of poly(styrenesulfonate)-functionalized multiwalled carbon nanotubes (MWCNT-PSS). Morphological analysis of the resulting CNT-PSS poly (3,4-ethylenedioxythiophene) (PEDOT) composites revealed the presence of PSS on the outer surface of the tubes with a core-shell structure and the association of PEDOT with the PSS bound to CNT. In comparison to the control PEDOT: PSS films, the composite film showed improved electrical properties along with high thermal stability, thus demonstrating its potential for application to robust optoelectronic devices. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3231486] All rights reserved.