Composite films of poly(o-methoxyaniline) (POMA) and carbon nanotubes (CNTs) were prepared via electrochemical co-deposition from the aqueous solutions containing o-methoxyaniline and acid-treated CNTs. The addition of small amounts of CNTs to o-methoxyaniline can accelerate significantly the electrochemical polymerization rate of the monomer. As-prepared composite films are characterized by thermal analysis, SEM, and the electrochemical methods. The results of the thermal analysis show that the composites have an enhanced thermal stability relative to POMA. SEM revealed that CNTs had been uniformly coated with POMA, forming dense nanoporous networks composite films.