Here, we report a facile hydrothermal synthesis method to prepare BiFeO3 nanowire-reduced graphene oxide (BFO-RGO) nanocomposites. The unique properties of 2-D reduced graphene oxide (RGO) and 1-D BiFeO3 nanowires (BFO) were exploited to design nanocomposites to obtain high performing microwave absorber materials. The composite with 97 wt % BFO and 3 wt % RGO exhibited minimum reflection loss value of -28.68 dB at 10.68 GHz along with the effective absorption bandwidth (≥ -10 dB) ranging from 9.6 to 11.7 GHz when the absorber thickness was only 1.55 mm. Firstprinciples calculations based on density functional theory (DFT) of BFO, graphene, and BFO-RGO nanocomposites were performed to obtain information about their electronic structures to interpret their complex permittivity and its derived properties. To the best of our knowledge, this is the first time investigations on microwave absorption properties of the BiFeO3 nanowire and BFO-RGO nanocomposites have been reported, and this nanocomposite shows its potential to be used as a lightweight, high performing microwave absorber in the X-band region. © 2017 American Chemical Society.