In this work, a new platinum (Pt) nanoparticles-functionalized poly(diallyl dimethyl ammonium chloride) (PDDA)-diamond powder (DMP) composite-modified glassy carbon electrode (GCE) was fabricated for electrochemical sensing of the selective or simultaneous determination of bisphenol A (BPA) and bisphenol S (BPS). The Pt/PDDA-DMP hybrid was characterized by Scanning electron microscopy, Transmission electron microscope, Fourier transform infrared, X-ray diffraction analyzer. This hybrid exhibited remarkable electrocatalytic activity towards the oxidation of BPA and BPS. The simultaneous determination of BPA and BPS by cyclic voltammetry yielded a difference of 0.316 V, which was sufficiently large for their potential recognition and simultaneous detection in mixtures. Differential pulse voltammetry was successfully used to simultaneously quantify BPA and BPS within the concentration range of 5-30 and 10-60 mu M under optimal conditions, respectively. The detection limits (S/N = 3) of Pt/PDDA-DMP/GCE for BPA and BPS were 0.6 and 2.0 mu M, respectively. The fabricated electrode showed good sensitivity, stability, and selectivity. The proposed method was successfully applied to determine BPA and BPS in biological samples. (C) The Author(s) 2016. Published by ECS. All rights reserved.