Abstract Epoxy/multiwall carbon nanotubes (MWCNTs) composites were investigated using three different non-ionic surfactants (BYK-110, Tween-80 and Nonidet-P40) separately as a modifier. The role of surfactants in dispersion of MWCNTs in the epoxy matrix was studied. Among three surfactants used, performance of Nonidet-P40 was found to be the best in improving the thermomechanical properties of the epoxy resin and achieving good dispersion of MWCNTs. The good dispersion of Nonidet-P40 modified MWCNT in the epoxy matrix is a result of the π–π interaction between π electrons of the Nonidet-P40 and π electron clouds of MWCNTs as well as H-bonding interaction between of Nonidet-P40 and the epoxy matrix. This type of interaction does not disturb the π electron clouds of MWCNTs as opposed to chemical functionalization strategy.