Electroactive copolymers of o-toluidine (OT) and o-phenylenediamine (OPD) were electrosynthesized in aqueous sulfuric acid. Cyclic voltammetry was used both for the electrochemical synthesis and characterization of the copolymers deposited on a gold electrode. The voltammograms exhibited different behavior for different concentrations of OPD in the feed. At optimum conditions the rate of copolymerization was found to be between the rates of homopolymerizations. The resulting poly(OPD-co-OT) shows an extended useful potential range of the redox activity as compared to the corresponding homopolymers. The effect of scan rate and pH on the electrochemical activity was studied. The copolymer was electrochemically active even at pH 9.0. In situ conductivity measurements further support the formation of a copolymer because the copolymers have a potential region of maximum conductivity completely different from that of POT. However, conductivities of the copolymers were lower by 2–2.7 orders of magnitude than of POT.