Polybrominated diphenyl ethers (PBDEs) are a type of flame retardants which are currently banned in EU and USA due their hazardousness for humans and mammals. However, these compounds were highly used during more than 30 years and still persist in the environment since they are resistant to degradation. Herein we present a biosensor for the detection of PBDEs using screen printed carbon electrodes (SPCEs) based on the electrochemical monitoring of water oxidation reaction (WOR) catalyzed by iridium oxide (IV) nanoparticles(IrO2 NPs). Our assay shows a limit of detection of 21.5 ppb of PBDE in distilled water. We believe that such an IrO2 NPs-based electrocatalytic sensing system can lead to a rapid, sensitive, low cost and miniaturizable device for the detection of PBDEs.