Abstract: Unidirectional carbon fiber/reduced graphene oxide nanosheet-epoxy laminate composites (CF/RGONs-epoxy) were produced by impregnating the CFs with epoxy acetone solutions containing RGONs, followed by solvent evaporation and curing at 180℃ under 0.6 MPa. The RGONs were prepared by the Hummers method and reduced to different oxygen contents using hydrazine monohydrate by adjusting the reduction temperature. The effect of the content of RGONs on the mechanical properties and electromagnetic interference (EMI) shielding effectiveness of the composites was investigated. Results indicate that in contrast to the detrimental effect of GO on the flexural and thermal properties, the addition of RGONs improves the mechanical property and EMI shielding effectiveness of the composites without sacrificing their thermal properties. RGONs with a relatively lower oxygen content show more apparent mechanical reinforcement while RGONs with a relatively higher oxygen content show a more obvious improvement on EMI shielding effectiveness. The improved interfacial properties are mainly ascribed to the toughening effects of the RGONs.