Despite many important industrial applications, the acrylonitrile-butadiene-styrene copolymer (ABS) suffers from an inherent flammability, extremely hampering its practical use. Current flame retardants can effectively reduce the flammability issue but give rise to degraded mechanical and thermal properties of ABS. To address this intractable challenge, a graphene-derived flame retardant (Mo5/PN-rGO) was designed by introducing the functional elements (phosphorus, nitrogen and molybdate) onto the graphene oxides nanosheets. The resultant ABS nanocomposite containing 1.0 wt % of Mo5/PN-rGO exhibits a 28% increase in the tensile strength and a 58% enhancement in the Young’s modulus as compared to the ABS host. Furthermore, the glass transition temperature (T_g) increases by ca. 12 ^oC while the onset thermal decomposition temperature is significantly delayed by ca. 21 ^oC. In addition, the final ABS nanomaterial shows a 20 % reduction in the total heat release and a 45% decrease in the total smoke production in comparison to the ABS bulk. This work paves a new way for the creation of high-performance flame retardants towards advanced flame-retardant polymer nanocomposites with expandable industrial applications.