The objective of this study was to prepare an electromagnetic interference shielding material, water-borne polyurethane (WPU) filled with silver-nanoparticle-decorated functional reduced graphene oxide (Ag@FRGO). Functional reduced graphene oxide (FRGO) was functionalized through free radical polymerization before chemical reduction to prevent restacking and aggregation during the reduction. After the functionalization, the homogeneous dispersion of FRGO promoted the formation of conductive networks throughout the WPU matrix. To enhance the electrical conductivity and EMI SE of the composites, silver nanoparticles (Ag NPs) were deposited on the FRGO surface. Subsequently, WPU composites were synthesized through the solution-mixing method. Their microstructure, morphology, electrical conductivity and EMI SE were investigated, and the results showed that, among Ag@FRGO/WPU composite with different values for the weight ratio of Ag NPs to FRGO, the Ag@FRGO/WPU composite with 5 wt% FRGO and weight ratio of Ag to NPs of 10:1 (10Ag@FRGO/WPU) exhibited the highest electrical conductivity (25.52 S/cm) and an EMI SE of 35 dB in the frequency range of 8.2–12.4 GHz (X-band).