Multiwalled carbon nanotubes/cyanate ester composite using epoxy group as a bridge was prepared. After a two-step functionalization, the epoxy groups were introduced on the surface of multiwalled carbon nanotubes (MWNTs) successfully, which was confirmed by X-ray diffraction and Fourier transform infrared spectra. The mechanical and thermal properties of the cured cyanate ester resin and MWNTs/cyanate ester composites were examined by mechanical tests, scanning electron microscopy, and dynamic mechanical thermal analysis. The results showed that 2 wt% functionalized MWNTs can enhance the flexural strength and impact strength significantly and increase the glass transition temperature (T-g) slightly. POLYM. ENG. SCI., 49:680-684, 2009. (c) 2009 Society of Plastics Engineers