In this work, nitrogen-doped reduced graphene oxide/nickel ferrite (NRGO/NiFeO) hybrid nanocomposites were synthesized by a one-pot hydrothermal method. Results manifested that the as-synthesized NiFeO nanoparticles displayed hexagonal morphology with a mean size of 40 nm. Moreover, it was found that the entangled structure consisting of crumpled RGO and hexagonal NiFeO nanoparticles was well constructed in the as-fabricated hybrid nanocomposites. Furthermore, the additive volumes of hydrazine hydrate and filler loadings had significant influences on the electromagnetic wave (EMW) absorption properties of obtained nanocomposites. Remarkably, the NRGO/NiFeO hybrid nanocomposite with 15 mL additive volume of hydrazine hydrate showed the optimal reflection loss of -54.4 dB at 9.2 GHz (X band) under a matching thickness of 2.2 mm and maximum absorption bandwidth of 4.5 GHz (13.5-18 GHz) at a very thin thickness of only 1.5 mm. The dual absorption peaks located at the low and high frequency regions could be achieved by facilely modulating the matching thicknesses. In addition, the underlying EMW absorption mechanisms were uncovered. Therefore, our results could shed light on the design and fabrication of graphene-based dielectric/magnetic hybrid composites as light-weight and high-efficiency EMW absorbers.