Urchinlike Ni nanoparticles/reduced graphene oxide (u-Ni/RGO) composites were successfully synthesized through a facile and effective one-pot solvothermal method to reduce graphene oxide (GO) and nickel salt with hydrazine hydrate in ethylene glycol (EG). The TEM and SEM images display that plenty of urchinlike Ni nanoparticles are deposited on the reduced graphene oxide (RGO) nanosheets. The magnetic hysteresis measurement reveals the ferromagnetic behavior of the composites at room temperature. The resulting electromagnetic (EM) absorption properties show that the maximum reflection loss of u-Ni/RGO composites is up to -32.1 dB at 13.8 GHz and the absorption bandwidth with the reflection loss less than -10 dB is 4.5 GHz (from 10.9 to 15.4 GHz) with the thickness of 2 mm. Interestingly, the reflection loss curve exhibits two obvious peaks corresponded to the reflection loss with the thickness of 4.0-5.0 mm. The remarkable EM absorption properties of u-Ni/RGO composites can be attributed to the multiple absorbing mechanisms. It is believed that such composites could serve as an attractive candidate for EM absorber. (C) 2014 Elsevier B.V. All rights reserved.