This paper reports on the synthesis and characterization (electrical, mechanical, thermal and dynamic mechanical) of electrically conducting polymer composites based on thermoplastic matrices (low density polyethylene (LDPE) and polypropylene (PP)) and two conducting fillers: iron particles (Fe) and carbon black (CB). The addition of Fe allows the easy incorporation of higher amounts of CB. Results suggest that the electrical and mechanical properties of these materials are improved by the presence of both fillers being necessary the addition of CB to achieve interesting values of conductivity. On the other hand, the crystalline structure of the polymer matrix is gradually reduced with the incorporation of both fillers but Fe by itself does not affect the geometry of growing crystals.