In this study, γ-Al2O3-GO, and γ-Al2O3-RGO nanocomposites were synthesized by the microwave-assisted coprecipitation method to study their electrical properties. X-ray diffraction pattern and energy-dispersive X-ray analysis confirmed that the nanocomposites successfully were synthesized. Transmission electron microscopy studies confirmed that γ-Al2O3 NPs formed into spherical particles and that these particles were dispersed randomly on RGO in contrast to γ-Al2O3-GO and Al2O3. At room temperature, the frequency dependence of the dielectric constant, dielectric loss, and AC conductivity of the synthesized samples were studied. Our findings indicate that the prepared nanocomposite RGO-Al2O3 has a dielectric constant of 16 at 106 Hz, which is twice the dielectric constant of commercially available Al2O3 which is mainly due to a more conductive network.