A review is presented of methods for enhancing the matrix-dominated thermomechanical properties of carbon/epoxy composites by incorporating carbon nanoparticles in the matrix. The materials used were DGEBA epoxy as the basic resin, carbon nanoplatelets, and multi-wall carbon nanotubes. With the latter, a block copolymer dispersant was used to optimize dispersion of the nanotubes. Preforms used were unidirectional carbon fibers (AS4) and five-harness satin weave carbon fabric (AGP370-5H, Hexcel Corp.). Matrix-dominated thermo-mechanical properties measured were glass transition temperature, compressive modulus and strength, interlaminar shear strength, and in-plane shear properties. Several batches of composite materials were processed and evaluated. They included reference carbon/epoxy composites without nanoparticles, unidirectional carbon/epoxy with carbon nanoplatelets, and carbon fabric/epoxy composites with carbon nanotube loadings of 0.5 and 1 wt%, with and without a copolymer dispersant. Special processing methods were developed, employing solvent-based high shear mixing and sonication. Significant increases in matrix dominated properties were measured. Micromechanical models were proposed to explain the measured enhancements.