Au/poly[anthranilic acid-co-3-carboxy-N-(2-thenylidene)aniline/PVAc] [Au/P(ANA-co-CNTA)/PVAc] electrospun nanofibers were fabricated in different electrospinning media including acetone and dimethylformamide (DMF) for covalent immobilization of glucose oxidase (GOx). The surface of copolymer nanofibers was activated by EDC/NHS chemistry, and the presence of Au nanoparticles as tiny conduction centers inside the copolymer matrix enhanced the electrochemical properties. Morphology and composition of enzyme-immobilized nanofibers were characterized by scanning electron microscopy/energy-dispersive X-ray spectroscopy (EM/EDX) and atomic force microscope (AFM). The effective covalent binding of glucose oxidase onto the Au/P(ANA-co-CNTA)/PVAc nanofibers was also confirmed by FTIR-ATR and Raman spectroscopy. EIS measurements revealed that the charge transfer resistances of the enzyme-immobilized nanofibers were decreased with increasing amount of enzyme. The effect of electrospun nanofiber diameter on sensing properties of enzyme-functionalized nanofibers was investigated by EIS. The sensitivities of electrodes calculated from impedance measurement were 7.24 x 10(6) and 6.67 x 10(3) Omega mM(-1) cm(-2) for the Au/P(ANA-co-CNTA)/PVAc-GO(X) (DMF) and Au/P(ANA-co-CNTA)/PVAc-GO(X) (acetone), respectively. The impedance measurement results revealed that the linear range of Au/P(ANA-co-CNTA)/PVAc-GO(X) (DMF) was lower than Au/P(ANA-co-CNTA)/PVAc-GO(X) (acetone). It could be attributed that smaller fiber diameter resulted in the higher specific surface area. This contributes to increasing the number of available active sites and, thus, increasing the amount of the enzyme loading.