Multiwalled carbon nanotubes were modified by interaction with gamma-aminopropyltriethoxysilane and were dispersed in an epoxy compound. The properties of multiwalled carbon nanotubes treated with gamma-aminopropyltriethoxysilane were characterized by transmission electron microscopy and by Raman and Fourier IR spectroscopy. Multiwalled carbon nanotubes modified with gamma-aminopropyltriethoxysilane are uniformly distributed in the bulk of the epoxy compound. Introduction of modified carbon nanotubes into the epoxy compound initiates curing of the epoxy oligomer and, in addition, leads to reinforcement of epoxy composites: The bending strength increases by 194%, the bending elastic modulus, by 137%, the tensile strength, by 108%, the tensile elastic modulus, by 52%, and the impact resilience, by 300% relative to the plasticized epoxy composite without multiwalled carbon nanotubes.