Enzymatic synthesis of a conducting complex of polyaniline (PANI)-poly(vinylphosphonic acid) (PVP) Is presented. The polymerization of aniline was carried out in an aqueous buffer at pH 4.0 using the enzyme horseradish peroxidase (HRP) as the biocatalyst in the presence of a PVP polyanion template. The formation of the conducting and electroactive form of the PVP-PANI complex was confirmed through W-vis and FTIR spectroscopy, elemental analysis, four-point probe conductivity measurements, and thermogravimetric analysis. Appropriate control of polymerization could be used to tune the water solubility and conductivity of the final PVP-PANI macromolecular complex. This template-guided enzymatic reaction is a unique approach for the controllable polymerization of aniline to the electroactive form under milder and environmentally compatible conditions. In this work, PVP was chosen as the polyelectrolyte to demonstrate both versatility with other templates and as a proof-of-concept for extension of this approach to other more delicate phosphate/phosphonic acid containing biological polyelectrolytes such as DNA.