An electropolymerized film of new eriochrome black T (EBT) doped with carbon nanotubes (CNTs) has been prepared on the surface of indium tin oxide (ITO) in a solution of acetonitrile containing lithium perchlorate (LiClO$_4$) assupporting electrolyte by cyclic voltammetry (CV). The distribution of CNTs in the poly eriochrome black T (PEBT) matrix was studied through scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy. Their chemistry and electrical properties were determined by CV and electrochemical impedance spectroscopy (EIS). The optical characterization of the composites was made by UV–Vis absorption. The results showed that CNTs nanoparticles were dispersed and co-deposited into the PEBT matrix; the voltammogram of EBT before and after doping with the semiconductor of CNTs present a large difference in the form of recorded cyclic voltammograms. It is noticed that the shape (intensity, potential and number of redox couple) of the cyclic voltamperogram varies with the addition of CNTs; the appearance of new peaks of oxidation and reduction suggests the formation of a new composite material. This confirmed that there is a reaction which develops between the EBT, CNTs and LiClO$_4$. The best distinction of the peaks was obtained during the addition of 0.2 mg of CNTs, leading to increase the conductivity of the PEBT film that forms on the ITO electrode. The images of SEM confirm the presence of CNTs in the composite, which consequently modifies significantly the morphology of the film. The CV study showed redox couples characteristic of poly EBT at 0.6 and 0.5 V.The EIS measurements show that the resistance of the PEBT films decreases with increasing of CNTs amounts. This demonstrates that the inclusion of the CNTs enhance the electrical properties of the polymer. Thus, these composite films can be used in various fields. The optical bandgap decreased generally with increase in content of CNTs compared with PEBT only. This is explained by the introduction of the donor levels in the bandgap of PEBT by the CNTs, this decrease in gap energy is explained by the Burstein–Moss effect.