Over the past decade, poly(3,4-ethylenedioxythiophene) (PEDOT) has been one of the widely investigated conjugated polymers due to its excellent electro-optical properties. The conventional synthesis of PEDOT/PSS involves oxidation of EDOT using strong oxidants in aqueous polystyrenesulfonate (SPS) solution. The low pH conditions and strong oxidants render this synthetic protocol unsuitable for use of PEDOT in applications Such as biosensing. For the purpose of expanding the utility of PEDOT in these applications, it is important to develop a route that can provide the possibility of synthesizing PEDOT in the presence of the appropriate biological entities. Here we report the use of terthiophene as a radical mediator to synthesize PEDOT/PSS under milder pH conditions using soybean peroxidase (SBP). The oxidation potential of terthiophene is sufficiently low for initiation of the polymerization reaction catalyzed by SBP. The oxidized terthiophene helps the subsequent oxidation of EDOT, thus mediating the polymerization reaction. This novel approach involving the use of conjugated oligomers as redox mediators is generic and vastly expands the types of substrates (thiophenes, pyrroles) that can be polymerized using enzymatic methods and benign conditions.