Conducting poly (3-hexylthiophene) (P3HT) was synthesized electrochemically in aqueous medium and characterized by electrochemical impedance spectroscopy, Tafel, SEM and TEM. The antidepressants drugs diazepam (DIZ), nitrazepam (NITZ) and imipramine (Evil) were analyzed on nanosize P3HT modified glassy carbon electrode. The voltammetric behavior of the three antidepressants was studied in aqueous acid, neutral, and alkaline conditions. One well-defined reduction peak each for DIZ and NITZ and one oxidation peak for IMI were observed in the cyclic voltammograms. The influence of pH, scan rate on peak current was studied extensively. A systematic study of the experimental parameters that affect the differential pulse stripping voltammetric response was carried out and optimized conditions which yield maximum peak current were arrived. The calibration was made under optimum conditions. The range of study for DIZ, NITZ and IMI was 100-1100, 150-1100 and 200-1300 mu g/L and lower limit of determination was 75, 100, and 150 mu g/L respectively. The suitability of the method for the determination of the three antidepressants in pharmaceutical preparations and urine samples was also ascertained. (C) 2013 The Electrochemical Society. [DOI: 10.1149/2.005306jes] All rights reserved.