Reduced graphene oxide/zinc ferrite (RGO/ZnFe2O4) hybrid nanocomposite was fabricated by a facile solvothermal route. ZnFe2O4 nanoparticles with an average diameter around 10.2 nm were homogeneously anchored on the surface of RGO sheets without large aggregation. Moreover, the effect of filler content on the microwave absorption performance of the hybrid nanocomposite was explored in detail. The as-prepared hybrid nanocomposite exhibited excellent microwave absorption performance with the minimum reflection loss of 41.1 dB for a thickness of 2.5 mm and effective absorption bandwidth (less than 10 dB) of 3.2 GHz for a thickness of 2.0 mm. Our results indicated that the deposition of ZnFe2O4 nanoparticles on RGO sheets was an efficient way to fabricate RGO-based high-performance microwave absorbers.