In this work, a novel sandwiched film of cadmium sulphide/reduced graphene oxide (CdS/r-GO) was synthesized via one step hydro-thermal reaction and electrodes modified with this composite were successfully used to simultaneously determine hydroquinone (HQ), catechol (CC) and resorcinol (RC). Additionally, some kinetic parameters, such as the charge transfer coefficient (α) and the electron transfer rate constant (k_s) were calculated. Differential pulse voltammetry (DPV) was used for the simultaneous determination of HQ, CC and RC in their ternary mixture. The calibration curves of HQ, CC and RC were obtained in the ranges of 0.2 to 2300 μM, 0.5 to 1350 μM and 1.0 to 500 μM, respectively. The detection limits for HQ, CC and RC were 0.054 μM, 0.09 μM and 0.23 μM, respectively (S/N = 3). The modified electrode was then used to analyse tap water, well water and river water and the results show its significance for practical applications in the aquatic environment.