The failure analysis of reinforcing elements is of great significance to understand the structure-property relationship in polymer composites. Herein, we reported an improved methodology to ascertain and contrast the failure modes from one pair of homologous fracture surfaces of multi-walled carbon nanotubes (MWCNTs)/epoxy samples at high-magnification using scanning electron microscopy. Three possible failure modes of MWCNTs, i.e. pullout, immediate fracture and sliding-fracture, were proposed to account for the fractographic observation. Based on this approach, the failure modes of MWCNTs before and after surface modification were quantitatively discussed. (C) 2011 Elsevier Ltd. All rights reserved.