The impediments to incorporating graphene into poly(vinyl alcohol) (PVA) are intrinsically inhomogeneous dispersion and agglomeration during mixing. Two types of PVA composites containing reduced graphene oxide (r-GO) and a novel aryl diazonium salt functionalized graphene (ADS-G) as nanofiller were successfully prepared by a simple solution casting. Fourier transform infrared spectroscopy showed the reduction of graphene oxide (GO), chemical functionalization of graphene by ADS, and formation of graphene-based PVA composites. Field emission scanning electron microscopy and transmission electron microscopy image analyses indicated that r-GO and ADS-G were fully incorporated into the PVA matrix. ADS-G formed better dispersion than r-GO and acted as good reinforcing filler to enhance the mechanical and dielectric properties of PVA. The tensile strength and modulus of the resulting PVA/ADS-G composites were improved by about 181% and 198%, respectively. In contrast, the tensile strength and modulus of PVA/r-GO composites were enhanced by 125% and 160%, respectively. The electrical conductivities were increased by 107 orders of magnitude in the composites with only 1.0 wt.% of filler loadings as compared to that of neat PVA. PVA/ADS-G composites showed greater improvement in thermal stability than PVA/r-GO composites, as evidenced from thermogravimetric and differential scanning calorimetric analyses. These results demonstrated that the ADS-G acted as good reinforcing filler compared to r-GO when using PVA as a polymer matrix. (C) 2014 Elsevier B.V. All rights reserved.