Conductive polyoxymethylene/polythiophene (POM/PT) composites and PT/POM blends were prepared by in situ chemical polymerization using FeCl3 oxidant and mixing in solutions, respectively. It was found that the properties of the composites and blends were different from those of homopolymers and also from each other. Formation of polymer and composites was supported by FT-IR analyses. According to the results of thermal analyses (TGA), it was shown that polymers and composites have good thermal stability. The thermal degradation temperature of POM/PT composite containing 88% PT is higher than those of the other composites. The thermal degradation temperature of PT/POM blend containing 27% POM was described as higher than that of the other blends. The morphological structures of polymers and composites were studied by scanning electron microscopy (SEM). It was found that morphological structures of composites were smoother than that of PT. The crystal structures of polymers and composites were investigated by X-ray diffraction analysis. It was found that the crystal regions increased with increasing amount of POM in the composites and blends.