Core-shell nanostructured polythiophene-multiwalled carbon nanotube nanocomposites (PT-CNTs) have been synthesised by in-situ chemical oxidative polymerization of thiophene in presence of multiwalled carbon nanotubes (MWCNT) and anionic surfactant sodium bis(2-ethylhexyl) sulfosuccinate (AOT) using ferric chloride as an oxidizing agent in chloroform solution. Nanocomposites were prepared by introducing different weight percentage amount of MWCNT into a fixed monomer and surfactant composition. The formations of the polythiophene-multiwalled carbon nanotube nanocomposites have been characterised by fourier transform infrared spectroscopy and elemental analysis. Sodium bis(2-ethylhexyl) sulfosuccinate (AOT) has been used as dopant cum template for polythiophene and polythiophene-multiwalled nanocomposite preparation. WXRD studies reveal that polythiophene shows a broad peak at 2 theta value 18.23 degrees. On the other hand, PTCNT nanocomposites were shown a sharp peak at 2q value 26.48 degrees and the broad peak present in polythiophene was completely vanished upon nanocomposite formation. The scanning electron microscopic (SEM) analysis of the samples reveals that PTCNT nanocomposites have a fiber like nanostructures. The core-shell nanostructure formation was confirmed by transmission electron microscopy (TEM) analysis. The outer shell thickness of the carbon nanotubes in nanocomposite increases approximately 3 to 15 nm from the original thickness after the formation of nanocomposite. The PTCNT samples synthesised in presence of AOT were easily dispersed in chloroform, which enabled us to carry out the UV-Visible absorption spectroscopy. The characteristic absorption peak present at 340 nm corresponds to the pi-polaron transition of polythiophene. The formation mechanism of core-shell nano structured composites was proposed based on the evidence from SEM, TEM, WXRD and spectroscopic studies. The four probe electrical conductivities of PTCNT samples were of the order of 1.5 times higher in magnitude than PT samples. (C) 2016 Elsevier Ltd. All rights reserved.