Multi-walled carbon nanotubes (MWCNTs), surface-treated via chemical functionalization, i.e., oxidation and amidation, were used to reinforce diglycidylether of bisphenol F (DGEBF) epoxy resin. The effects of the functionalization on the dispersion stability, rheological properties, and fracture toughness of DGEBF/MWCNT composites were investigated. The dispersion homogeneity of the MWCNTs in the epoxy matrix improved after functionalization. In addition, isothermal rheology measurements revealed that the DGEBF/dodecyl amine-functionalized MWCNT (D-MWCNT) composite had a longer gel time and higher activation energy of cross-linking than the DGEBF/acid-treated MWCNT (A-MWCNT) composite. The fracture toughness of the former was also significantly higher than that of the latter; this resulted from the relatively high dispersion stability of the D-MWCNTs in the epoxy matrix, owing to the presence of alkyl groups on the D-MWCNT surface. POLYM. ENG. SCI., 55:2676-2682, 2015. (c) 2015 Society of Plastics Engineers