In the present study, a novel enzymatic glucose biosensor using glucose oxidase (GOx) immobilized into (3-aminopropyl) triethoxysilane (APTES) functionalized reduced graphene oxide (rGO-APTES) and hydrogen peroxide sensor based on rGO-APTES modified glassy carbon (GC) electrode were fabricated. Nafion (Nf) was used as a protective membrane. For the characterization of the composites, Fourier transform infrared spectroscopy (FTIR), X-ray powder diffractometer (XRD), and transmission electron microscopy (TEM) were used. The electrochemical properties of the modified electrodes were investigated using electrochemical impedance spectroscopy, cyclic voltammetry, and amperometry. The resulting Nf/rGO-APTES/GOx/GC and Nf/rGO-APTES/GC composites showed good electrocatalytical activity toward glucose and H2O2, respectively. The Nf/rGO-APTES/GC electrode exhibited a linear range of H2O2 concentration from 0.05 to 15.25 mM with a detection limit (LOD) of 0.017 mM and sensitivity of 124.87 mu A mM(-1)cm(-2). The Nf/rGO-APTES/GOx/GC electrode showed a linear range of glucose from 0.02 to 4.340 mM with a LOD of 9 mu M and sensitivity of 75.26 mu A mM(-1)cm(-2). Also, the sensor and biosensor had notable selectivity, repeatability, reproducibility, and storage stability.