In-situ interfacial polymerization method was employed to synthesize nanocomposites based on a semi-aromatic polyamide (PA) and pristine or sulfonated graphene oxides (GO or SGO, respectively). The PA chains were produced at the interface of a nonaqueous solution of isophthaloyl dichloride and an aqueous triethylenetetramine solution containing different amounts of GO or SGO dispersed nanosheets. The effects of SGO and pristine GO on the structure, thermal stability and dynamic mechanical and electrical properties of PA were studied. Favorable interfacial interactions between SGO and PA were confirmed using Fourier transform infrared spectroscopy and X-ray diffractometry. Consequently, SGO significantly increased the thermal stability and char residues of PA. Furthermore, adding both pristine and sulfonated GO nanosheets led to an enhancement in storage modulus and a shift in glass transition temperature of the polyamide. Finally, the facile sulfonation of GO resulted in partial reduction of the electrically insulating nanosheets and hence the electrical conductivity and dielectric constant of PA were increased by 10 and 3 times, respectively, at SGO content of 1.0 wt%.