The incorporation of free transition metal cations (potential redox catalyst centers) into conducting organic films by electrodeposition is relatively rare due to the repulsive nature of the positive cation radicals of the polymer itself during polymerization. This paper shows that such metal cations can be trapped in the polymer matrix as it is being electrodeposited on a metal substrate electrode, which itself simultaneously electro-oxidizes (corrodes). The electropolymerization of 3-methylthiophene on Mo(0), Ni(0) and Fe(0) substrate electrodes (’active electrodes’) is reported. SEM, EDXRF, and XPS were used to demonstrate the amount of metal cations in and/or on the polymer matrix and to determine the valence states. The rates of diffusion of the incorporated metal ions into an LiClO4 electrolyte solution were also studied. The presence of trace amounts of all three metal cations were sufficient to destroy the electroactivity of the polymer film electrodes for the oxidation of catechol.