An electrochemical sensor based on graphene-Nafion nanocomposite film for voltammetric determination of acetaminophen (APAP) was presented. A Nafion graphene oxide-modified glassy carbon electrode was fabricated by a simple drop-casting method and then graphene oxide was reduced at the glassy carbon electrode surface by electrochemical method. The resulting electrode [electrochemically reduced graphene oxide (ER-GO)/Nafion glassy carbon electrode (GCE)] was used to determine acetaminophen. The electrochemical behaviors of acetaminophen on Nafion/ER-GO modified glassy carbon electrodes (GCEs) were investigated by cyclic voltammetry and square-wave voltammetry. The results obtained that the Nafion/ER-GO/GC modified electrode was exhibited excellent electrochemical activity on the oxidation of APAP. The calibration curve for APAP was shown two linear segments: the first linear segment increases from 0.4 to 1.0 and second linear segment increases up to 10 mu M. The detection limit was determined as 0,025 mu M (2.5x10(-8) mol L-1) using SWV. Finally, the proposed method was successfully used to determine APAP in pharmaceutical preparations and urine samples.