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 μM 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 μM, respectively. The fabricated electrode showed good sensitivity, stability, and selectivity. The proposed method was successfully applied to determine BPA and BPS in biological samples. Bisphenol A (BPA) [2,2-bis (4-hydroxyphenyl) propane (C 15 H 16 O 2 )] is an important chemical raw material that is widely used in industrial production and daily life.1-3 It is extensively used in food cans, packing materials, water bottles, and baby bottles. As an environmental hormone material that causes abnormal hormone activity, BPA causes irreversible damage to organisms and the environment, and low doses can even result in human endocrine disorders. 5,6 In addition, BPA negatively affects female hormones, which can lead to a series of female diseases, such as induced precocious puberty, reproductive dysfunction, endometrial hyperplasia, and recurrent miscarriage. 7,8 Canada and China banned the use of BPA in baby bottles in 2010 and 2011, respectively, because of its negative effects on humans, particularly to children and infants. 9 In recent years, numerous companies and factories are currently using bisphenol S (BPS) [4,4 sulfomyldiphenol (C 12 H 10 O 4 S)] instead of BPA.10 BPS is widely used in polyethersulfone. The production and use of BPS as a chemical additive in pesticides, dyestuffs, colorfast agents, dye dispersants, and monomer in cyclic carbonates are increasing and will exceed those of BPA. 11,12 Although BPS has high thermal stability and low biodegradability, 13 it also has biological toxicity 14,15 and negative hormone effects.16,17 BPS and BPA disrupt the human endocrine system by interfering with several functional nuclear receptors.18 Thus, BPS is not a safe and reliable replacement for BPA. Several methods are available for state of the art tools for detecting BPS and BPA, such as automated on-line column-switching high performance liquid chromatography isotope dilution tandem mass spectrometry, 19 analytical paralysis gas chromatography mass spectrometry, 20 synchronous...