The evolution of high electromagnetic absorption materials is essential in the fast growing electronic industry in overcoming electromagnetic pollution. In view of this, a series of Ni nanoparticle-decorated functionalized graphene sheets (FG/Ni) are synthesized by a solvothermal method using different ratios of FG/Ni precursors. Subsequently, FG/Ni is subjected to in situ polymerization of aniline to form FG/Ni/PANI ternary composites and characterized. The total electromagnetic interference shielding efficiency (SET) measurements on FG/Ni/PANI with an optimized FG/Ni ratio (50 mg:600 mg NiCl2·6H2O) exhibit enhanced performance, i.e., ∼47-65 dB (2-3.8 GHz) and ∼65-45 dB (3.8-8 GHz), following absorption as the dominant mechanism due to the matching of dielectric loss and magnetic loss. It is anticipated that such excellent performance of robust FG/Ni/PANI ternary composites at a very low thickness (0.5 mm) has great potential in the application of microwave-absorbing materials.