The effect of multi-walled carbon nanotubes (MWCNTs) and processing methods on the morphological, dynamic mechanical, mechanical, thermal and electrical properties of MWCNT/nylon 6 (PA6) composites has been investigated. The MWCNTs have been functionalized covalently and noncovalently for better dispersion in the polymer matrix. A homogeneous dispersion of MWCNTs was achieved in the PA6 matrix as evidenced by scanning electron microscopy. The strong interaction between the functionalized MWCNTs and the PA6 matrix greatly enhanced the dispersion as well as the interfacial adhesion. As a result, the overall mechanical performance of the composites could be improved. The incorporation of the MWCNTs effectively enhanced the crystallization of the PA6 matrix through heterogeneous nucleation. The present investigation revealed that the mechanical, thermal as well as electrical properties of MWCNT-filled polymer composites were strongly dependent on the state of dispersion, mixing and processing conditions, and interaction with the polymeric matrix. (C) 2009 Published by Elsevier B.V.