Both epoxy resin and acid-modified multiwall carbon nanotube (MWCNT) were treated with 3-isocyanatopropyltriethoxysilane (IPTES). Scanning electron microscopy (SEM) and transmission electronic microscope (TEM) images of the MWCNT/epoxy composites have been investigated. Tensile strength of cured silane-modified MWCNT (1.0 wt%)/epoxy composites increased 41% comparing to the neat epoxy. Young's modulus of cured silane-modified MWCNT (0.8 wt%)/epoxy composites increased 52%. Flexural strength of cured silane-modified MWCNT (1.0 wt %)/epoxy composites increased 145% comparing to neat epoxy. Flexural modulus of cured silane-modified MWCNT (0.8 wt %)/epoxy composites increased 31%. Surface and volume electrical resistance of MWCNT/epoxy composites were decreased with IPTES-MWCNT content by 2 orders and 6 orders of magnitude, respectively. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 3481-3488, 2010