Carbon nanomaterials are receiving worldwide attention because of their multi-faceted superiority in thermal conductivity, flame retardancy, mechanical stability, electrical conductivity, and biocompatibility. In this review, a survey of the literature on extending performance of epoxy resins based on carbon nanomaterials is presented. The structure-performance relationships for different carbon nanomaterials modified epoxy are closely analyzed. The performance extension in mechanical, electrical, thermal conductivity, flame retardancy, antidegradation, and tribological properties of epoxy are reviewed in detail. Other application areas including biocompatibility, biodegradability, gas barrier properties, shape memory, and electromagnetic interference shielding are touched. The challenges and opportunities in carbon nanomaterials functionalized epoxy composites are also discussed.