Multifunctional graphene hydrogels have attracted great attention aimed at practical applications. Herein, the novel and bifunctional composite hydrogel containing reduced graphene-oxide nanosheets (RGO) and V2O5 nanobelts (RGO/V2O5) is successfully prepared for the first time. Surprisingly, tridimensional (3D) RGO/V2O5 composite hydrogels cannot only be used as high-performance electromagnetic (EM) wave absorbents; they also exhibit excellent properties suitable for supercapacitor electrodes. The composites exhibit a maximum absorption of up to −21.5 dB. In particular, a composite hydrogel showed a bandwidth of 6.63 GHz, corresponding to a reflection loss at −10 dB, which opens the possibility for the use of 3D graphene with other functional nanomaterials as lightweight and high-performance EM wave absorption materials. Remarkably, the composite hydrogel is capable of delivering a high specific capacitance of about 320 F g−1 at a current density of 1.0 A g−1.