The electrosynthesis of polythiophene (PTh) films containing dispersed Pt or Pt + Pb and its employment in the electrocatalytic oxidation of HCOOH (I) were studied. The influence of PTh film thickness, the amount of dispersed Pt particles, the amount of Pb deposited and the electrode rotation effects on the electro-oxidation of I was investigated. The electrodic system comprising PTh-Pt + Pb shows a better electrocatalytic activity than PTh-Pt and massive Pt electrodes. The current densities observed in the electro-oxidation of I do not depend on the solution stirring, and the presence of Pb2+ in the electrolyte was not required. Furthermore, a greater decrease in poisoning species during the electro-oxidation of I is achieved. By applying an E-t program, which took the oxidation of residual species and the electroadsorption of I into consideration, the activity of the PTh-Pt + Pb electrode was maintained over 36 h without variation. The role assumed by Pb in this electrode system is in accordance with the Pb adatom effect observed in massive Pt electrodes. The performance of the electrode system studied shows the possibility of its employment in fuel cells.