The present work reports preparation and characterization of a new potentiometric sensor for determination of Diclofenac (DCF) based on doped polypyrrole films. The response mechanism for the proposed sensor is based on incorporation of DCF anion into polypyrrole film during polymer electrochemical synthesis in order to form a membrane with selective potentiometric response for the dopant ion. It was observed that the sensor performance is dependent of the measurement parameters used in the synthesis process realized under galvanostatic conditions. So, using the best set of experimental conditions (electric current density of 0.045 mA cm(-2) and electric charge of 35 mC) the sensor exhibited a linear dynamic response in the concentration range from 3.1 x 10(-4) to 1.1 x 10(-2) mol L-1 of DCF with a slope 48.2 mV dec(-1) and a limit of detection of 1.9 x 10(-4) mol L-1. The method was successfully applied in the determination of DCF in pharmaceutical commercial samples with good correlation with result provided by official method. The effect of interference species on potentiometric response and morphologic characterization using microscopy of atomic force (AFM) has been also realized. (C) 2014 Elsevier B.V. All rights reserved.