A direct and nondestructive strategy for growing polymers from the surface of graphene is demonstrated. The technique involves the covalent attachment of an initiator via one-step cycloaddition of a diarylcarbene, followed by the polymerization of 2-hydroxyethyl methacrylate (HEMA) using atom transfer radical polymerization (ATRP). The functionalization strategy is shown to significantly increase the solubility of the resulting materials (PHEMA-G) and leave the structure of the graphene largely intact. Importantly, the PHEMA-G/poly(p-phenylene benzobisoxazole) (PBO) composite fibers could be obtained by a one-pot polymerization and dry-jet wet spinning process. The nanocomposite fibers exhibited a tensile strength of 3.22 GPa (51.2% higher than PBO) and Young's modulus of 139.3 GPa (33.7% higher than PBO) at very low PHEMA-G loading (1.0 wt %). This represents an excellent reinforcing efficiency, better than other reports of the graphene/PBO fibers system, and indicates that this material is suitable for applications in composite science.