A facile electrochemical sensor was developed by electrochemical deposition of PtIr nanoparticles on poly(3,4-ethylenedioxythiophene) (PEDOT) modified carbon fiber paper electrode (CFP). The modified electrodes were characterized by Field emission scanning electron microscopy (FESEM) with energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), RAMAN spectroscopy, Fourier transform infrared spectroscopy (FTIR) and electroanalytical techniques. PtIr-PEDOT modified CFP electrode was used successfully in the determination of an anti-hypertensive prodrug Olmesartan medoxomil (OM) at femtomolar (fM) level for the first time. Under optimal conditions, the prepared electrochemical sensor has shown broad linear range between 0.001 pM and 0.220 pM and superior detection limit of 3.42 fM was observed based on Differential pulse voltammetric (DPV) study. In addition, the designed electrochemical sensor was successfully demonstrated as a novel platform in the electrochemical determination of OM in human urine and pharmaceutical samples. (C) 2018 The Electrochemical Society.