Reduced graphene oxide (RGO) with a layered and porous structure was synthesized by thermal exfoliation of graphite oxide. Synthesized RGO is very light weight and flaky. The formation of RGO was studied using Fourier transform infrared and Raman spectroscopies, X-ray diffraction and scanning electron microscopy. Composites were prepared by dispersing 2%, 4% and 10% by weight of the synthesized RGO into nitrile butadiene rubber (NBR) matrix. Microwave absorption properties of RGO/NBR composites were investigated by measuring their complex permittivity and permeability by using waveguide method. Simulation studies show that 10 wt.% of graphene oxide in NBR matrix exhibits high values of reflection loss (>10 dB) over a wide frequency range 7.5-12 GHz and maximum loss is 57 dB at 9.6 GHz at a thickness of 3 mm. © 2011 Elsevier Ltd. All rights reserved.